Cure-on-demand moisture-curable urethane-containing fuel resistant prepolymers and compositions thereof

ABSTRACT

Cure-on-demand, moisture-curable, urethane-containing prepolymers having urethanes incorporated into a sulfur-containing prepolymer backbone and compositions thereof for use in sealant applications are disclosed. The cure-on-demand moisture-curable urethane-containing prepolymers are terminated with polyalkoxysilyl groups. The compositions contain a controlled-release moisture cure catalyst. Compositions containing the prepolymers provide cured sealants exhibiting improved tensile strength.

This application is a continuation-in-part of U.S. application Ser. No.14/200,687 filed on Mar. 7, 2014, which is incorporated by reference inits entirety.

FIELD

The present disclosure relates to cure-on-demand moisture-curableurethane-containing prepolymers and compositions thereof for use inaerospace sealant applications. The cure-on-demand moisture-curableurethane-containing prepolymers are terminated with polyalkoxysilylgroups and are curable in the presence of moisture. The compositionscontain a controlled release moisture cure catalyst. Compositionsincluding the moisture-curable urethane-containing prepolymers providecured compositions exhibit improved tensile strength and/or elongation.

BACKGROUND

Sealants useful in aerospace and other applications must satisfydemanding mechanical, chemical, and environmental requirements. Thesealants can be applied to a variety of surfaces including metalsurfaces, primer coatings, intermediate coatings, finished coatings, andaged coatings.

SUMMARY

Cure-on-demand sealant compositions having improved cured propertiescontaining moisture curable urethane-containing fuel resistanceprepolymers that incorporate urethane segments into the polymer backboneand that contain a controlled release moisture cure catalyst aredisclosed.

According to the present invention, compositions can comprise (a) amoisture-curable urethane-containing fuel resistant prepolymercomprising a reaction product of reactants comprising (i) anisocyanate-terminated urethane-containing adduct comprising the reactionproduct of reactants comprising a hydroxyl-terminated sulfur-containingadduct comprising the reaction product of reactants comprising a hydroxyvinyl ether and a thiol-terminated sulfur-containing prepolymer; and adiisocyanate; and (ii) a compound comprising a group reactive with anisocyanate group; and at least one polyalkoxysilyl group; and (b) acontrolled release moisture cure catalyst.

According to the present invention, compositions can comprise:

(a) a moisture-curable urethane-containing prepolymer comprising amoisture-curable urethane-containing prepolymer of Formula (2a), amoisture-curable urethane-containing prepolymer of Formula (2b), or acombination thereof:

R³⁰—C(═O)—NH—R²⁰—NH—C(═O)—[—R⁶⁰—C(═O)—NH—R²⁰—NH—C(═O)—]_(w)—R⁶⁰—C(═O)—NH—R²⁰—NH—C(═O)—R³⁰  (2a)

B{—V′—S—R⁵⁰—S(CH₂)₂—O—R¹³—O—[—C(═O)—NH—R²⁰—NH—C(═O)—R⁶⁰—]_(w)—C(═O)—NH—R²⁰—NH—C(═O)—R³⁰}_(z)  (2b)

wherein,

-   -   w is an integer from 1 to 100;    -   each R¹³ independently comprises C₂₋₁₀ alkanediyl;    -   each R²⁰ independently comprises a core of a diisocyanate;    -   each R³⁰ independently is a moiety comprising a terminal        polyalkoxysilyl group;    -   each R⁵⁰ independently comprises a core of a sulfur-containing        prepolymer;    -   each R⁶⁰ independently comprises a moiety having the structure        of Formula (3):

—O—R¹³—O—(CH₂)₂—S—R⁵⁰—S—(CH₂)₂—O—R¹³—O—  (3)

-   -   B represents a core of a z-valent, polyfunctionalizing agent        B(—V)_(z) wherein,        -   z is an integer from 3 to 6; and        -   each V is a moiety comprising a terminal group reactive with            a thiol group; and        -   each —V′— is derived from the reaction of —V with a thiol;            and

(b) a controlled release moisture cure catalyst.

According to the present invention, cured sealants can be prepared fromthe compositions of the present disclosure.

According to the present invention, parts can be sealed withcompositions of the present disclosure.

According to the present invention, methods of sealing a surface cancomprise providing a surface; applying a composition provided by thepresent disclosure to the surface; activating the controlled releasemoisture cure catalyst; and curing the composition to seal the surface.

Reference is now made to certain embodiments of compositions andmethods. The disclosed embodiments are not intended to be limiting ofthe claims. To the contrary, the claims are intended to cover allalternatives, modifications, and equivalents.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of a reaction scheme for preparingmoisture-curable urethane-containing prepolymers according to thepresent disclosure.

DETAILED DESCRIPTION

For purposes of the following description, it is to be understood thatembodiments provided by the present disclosure may assume variousalternative variations and step sequences, except where expresslyspecified to the contrary. Moreover, other than in the examples, orwhere otherwise indicated, all numbers expressing, for example,quantities of ingredients used in the specification and claims are to beunderstood as being modified in all instances by the term “about.”Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired properties to beobtained. At the very least, and not as an attempt to limit theapplication of the doctrine of equivalents to the scope of the claims,each numerical parameter should at least be construed in light of thenumber of reported significant digits and by applying ordinary roundingtechniques.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

Also, it should be understood that any numerical range recited herein isintended to include all sub-ranges encompassed therein. For example, arange of “1 to 10” is intended to include all sub-ranges between (andincluding) the recited minimum value of about 1 and the recited maximumvalue of about 10, that is, having a minimum value equal to or greaterthan about 1 and a maximum value of equal to or less than about 10.Also, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

A dash (“-”) that is not between two letters or symbols is used toindicate a point of covalent bonding for a substituent or between twoatoms. For example, the chemical group —CONH₂ is covalently bonded toanother chemical moiety through the carbon atom. The expression “-” canbe used to denote the point of bonding.

“Alkanearene” refers to a hydrocarbon group having one or more aryland/or arenediyl groups and one or more alkyl and/or alkanediyl groups,where aryl, arenediyl, alkyl, and alkanediyl are defined herein. Eacharyl and/or arenediyl group(s) can be C₆₋₁₂, C₆₋₁₀, phenyl orbenzene-diyl. Each alkyl and/or alkanediyl group(s) can be C₁₋₆, C₁₋₄,C₁₋₃, methyl, methanediyl, ethyl, or ethane-1,2-diyl. An alkanearenegroup can be C₄₋₁₈ alkanearene, C₄₋₁₆ alkanearene, C₄₋₁₂ alkanearene,C₄₋₈ alkanearene, C₆₋₁₂ alkanearene, C₆₋₁₀ alkanearene, or C₆₋₉alkanearene. Examples of alkanearene groups include diphenyl methane.

“Alkanearenediyl” refers to a diradical of an alkanearene group. Analkanearenediyl group can be C₄₋₁₈ alkanearenediyl, C₄₋₁₆alkanearenediyl, C₄₋₁₂ alkanearenediyl, C₄₋₈ alkanearenediyl, C₆₋₁₂alkanearenediyl, C₆₋₁₀ alkanearenediyl, or C₆₋₉ alkanearenediyl.Examples of alkanearenediyl groups include diphenyl methane-4,4′-diyl.

“Alkanediyl” refers to a diradical of a saturated, branched orstraight-chain, acyclic hydrocarbon group, having, for example, from 1to 18 carbon atoms (C₁₋₁₈), from 1 to 14 carbon atoms (C₁₋₁₄), from 1 to6 carbon atoms (C₁₋₆), from 1 to 4 carbon atoms (C₁₋₄), or from 1 to 3hydrocarbon atoms (C₁₋₃). It can be appreciated that a branchedalkanediyl has a minimum of three carbon atoms. An alkanediyl can beC₂₋₁₄ alkanediyl, C₂₋₁₀ alkanediyl, C₂₋₈ alkanediyl, C₂₋₆ alkanediyl,C₂₋₄ alkanediyl, or C₂₋₃ alkanediyl. Examples of alkanediyl groupsinclude methane-diyl (—CH₂—), ethane-1,2-diyl (—CH₂CH₂—),propane-1,3-diyl and iso-propane-1,2-diyl (e.g., —CH₂CH₂CH₂— and—CH(CH₃)CH₂—), butane-1,4-diyl (—CH₂CH₂CH₂CH₂—), pentane-1,5-diyl(—CH₂CH₂CH₂CH₂CH₂—), hexane-1,6-diyl (—CH₂CH₂CH₂CH₂CH₂CH₂—),heptane-1,7-diyl, octane-1,8-diyl, nonane-1,9-diyl, decane-1,10-diyl,and dodecane-1,12-diyl.

“Alkanecycloalkane” refers to a saturated hydrocarbon group having oneor more cycloalkyl and/or cycloalkanediyl groups and one or more alkyland/or alkanediyl groups, where cycloalkyl, cycloalkanediyl, alkyl, andalkanediyl are defined herein. Each cycloalkyl and/or cycloalkanediylgroup(s) can be C₃₋₆, C₅₋₆, cyclohexyl or cyclohexanediyl. Each alkyland/or alkanediyl group(s) can be C₁₋₆, C₁₋₄, C₁₋₃, methyl, methanediyl,ethyl, or ethane-1,2-diyl. An alkanecycloalkane group can be C₄₋₁₈alkanecycloalkane, C₄₋₁₆ alkanecycloalkane, C₄₋₁₂ alkanecycloalkane,C₄₋₈ alkanecycloalkane, C₆₋₁₂ alkanecycloalkane, C₆₋₁₀alkanecycloalkane, or C₆₋₉ alkanecycloalkane. Examples ofalkanecycloalkane groups include 1,1,3,3-tetramethylcyclohexane andcyclohexylmethane.

“Alkanecycloalkanediyl” refers to a diradical of an alkanecycloalkanegroup. An alkanecycloalkanediyl group can be C₄₋₁₈alkanecycloalkanediyl, C₄₋₁₆ alkanecycloalkanediyl, C₄₋₁₂alkanecycloalkanediyl, C₄₋₈ alkanecycloalkanediyl, C₆₋₁₂alkanecycloalkanediyl, C₆₋₁₀ alkanecycloalkanediyl, or C₆₋₉alkanecycloalkanediyl. Examples of alkanecycloalkanediyl groups include1,1,3,3-tetramethylcyclohexane-1,5-diyl and cyclohexylmethane-4,4′-diyl.

“Alkenyl” refers to a group having the structure —CR═CR₂ where thealkenyl group can be a terminal group and is bonded to a largermolecule. In such embodiments, each R may be selected from, for example,hydrogen and C₁₋₃ alkyl. Each R can be hydrogen and an alkenyl group canhave the structure —CH═CH₂.

“Alkoxy” refers to a —OR group where R is alkyl as defined herein.Examples of alkoxy groups include methoxy, ethoxy, n-propoxy,isopropoxy, and n-butoxy. An alkoxy group can be C₁₋₈ alkoxy, C₁₋₆alkoxy, C₁₋₄ alkoxy, or C₁₋₃ alkoxy.

“Alkyl” refers to a monoradical of a saturated, branched orstraight-chain, acyclic hydrocarbon group having, for example, from 1 to20 carbon atoms, from 1 to 10 carbon atoms, from 1 to 6 carbon atoms,from 1 to 4 carbon atoms, or from 1 to 3 carbon atoms. It will beappreciated that a branched alkyl has a minimum of three carbon atoms.An alkyl group can be C₁₋₆ alkyl, C₁₋₄ alkyl, or C₁₋₃ alkyl. Examples ofalkyl groups include methyl, ethyl, n-propyl, iso-propyl, n-butyl,iso-butyl, tert-butyl, n-hexyl, n-decyl, tetradecyl, and the like. Analkyl group can be C₁₋₆ alkyl, C₁₋₄ alkyl, or C₁₋₃ alkyl. It can beappreciated that a branched alkyl can have at least three carbon atoms.

“Aminosilane” refers to a silane comprising an amine group.

“Cycloalkanediyl” refers to a diradical saturated monocyclic orpolycyclic hydrocarbon group. A cycloalkanediyl group can be C₃₋₁₂cycloalkanediyl, C₃₋₈ cycloalkanediyl, C₃₋₆ cycloalkanediyl, or C₅₋₆cycloalkanediyl. Examples of cycloalkanediyl groups includecyclohexane-1,4-diyl, cyclohexane-1,3-diyl, or cyclohexane-1,2-diyl.

“Cycloalkyl” refers to a saturated monocyclic or polycyclic hydrocarbonmonoradical group. A cycloalkyl group can be C₃₋₁₂ cycloalkyl, C₃₋₈cycloalkyl, C₃₋₆ cycloalkyl, or C₅₋₆ cycloalkyl.

“Heteroalkanediyl” refers to an alkanediyl group in which one or more ofthe carbon atoms are replaced with a heteroatom, such as N, O, S, or P.In a heteroalkanediyl, a heteroatom can be selected from N and O.

“Heteroalkanearenediyl” refers to an alkanearenediyl group in which oneor more of the carbon atoms are replaced with a heteroatom, such as N,O, S, or P. In a heteroalkanearenediyl, a heteroatom can be selectedfrom N and O.

“Heterocycloalkanediyl” refers to a cycloalkanediyl group in which oneor more of the carbon atoms are replaced with a heteroatom, such as N,O, S, or P. In a heterocycloalkanediyl, a heteroatom can be selectedfrom N and O.

“Derived from” refers to a functional group or moiety following reactionwith another reactive functional group or moiety. For example, themoiety —CH₂—CH₂—S— can be derived from the reaction of an alkenyl group,—CH═CH₂ with a thiol group —SH. Similarly, the moiety —S— can be derivedfrom the reaction of —SH with a group that is reactive with thiolgroups. A group —R′— can be derived from the reaction of the group —Rwith a reactive group.

A core of a sulfur-containing prepolymer or adduct refers to the moietyforming the sulfur-containing prepolymer or adduct without the terminalfunctional groups. For example, a sulfur-containing prepolymer or adductcan have the structure R^(f)—R—R^(f) where each R^(f) represents amoiety comprising a terminal functional group, and —R— represents thecore of the sulfur-containing prepolymer or adduct.

A core of a diisocyanate refers to the moiety forming the diisocyanatewithout the isocyanate groups. For example, the core of a diisocyanatehaving a structure O═C═N—R—N═C═O is represented by —R—.

“Moisture curable” prepolymers refer to prepolymers that are curable inthe presence of atmospheric moisture. Moisture curable prepolymersprovided by the present disclosure can be terminated in two or morepolyalkoxysilyl groups. An end of a moisture curable prepolymer may beterminated with one polyalkoxysilyl group, two polyalkoxysilyl groups,or three polyalkoxysilyl groups. Thus, a linear moisture-curableprepolymer may comprise from two to six polyalkoxysilyl groups. A linearmoisture-curable prepolymer may comprise a mixture of moisture-curableprepolymers having different numbers of polyalkoxysilyl groups andtherefore may be characterized by an average non-integer polyalkoxysilylfunctionality from two to six. A backbone of a moisture-curableprepolymer can be polyfunctional having, for example from three to sixarms. Each of the arms may be terminated in from one to threepolyalkoxysilyl groups. Thus, moisture-curable prepolymers having amulti-dentate backbone may have, for example, from 3 to 18polyalkoxysilyl groups. Linear and multi-dentate moisture-curableprepolymers having different numbers of polyalkoxysilyl groups may becombined in different ratios to provide moisture-curable prepolymerscharacterized by a wide range of polyalkoxysilyl functionality.

As used herein, “polymer” refers to oligomers, homopolymers, andcopolymers, which may be cured or uncured. Unless stated otherwise,molecular weights are number average molecular weights for polymericmaterials indicated as “M_(n)” as determined, for example, by gelpermeation chromatography using a polystyrene standard in anart-recognized manner. Unless stated otherwise, molecular weights arenumber average molecular weights for polymeric materials indicated as“Mn” as may be determined, for example, by gel permeation chromatographyusing a polystyrene standard in an art-recognized manner.

“Prepolymers” refer to polymers prior to curing. In general, prepolymersprovided by the present disclosure are liquid at room temperature.“Adducts” can refer to prepolymers that are functionalized with areactive terminal group; however, prepolymers may also contain terminalfunctional group. Thus, the terms prepolymer and adduct are usedinterchangeably. The term adduct is often used to refer to a prepolymerthat is an intermediate in a reaction sequence used to prepare aprepolymer.

“Polythioether” refers to a compound containing at least two thioetherlinkages, that is —C(R)₂—S—C(R)₂— groups. In addition to at least twothioether groups, polythioethers provided by the present disclosure maycomprise at least two formal, acetal, and/or ketal groups, e.g., atleast two —O—C(R)₂—O— groups, where each R can independently be selectedfrom hydrogen, C₁₋₆ alkyl, C₇₋₁₂ phenylalkyl, substituted C₇₋₁₂phenylalkyl, C₆₋₁₂ cycloalkylalkyl, substituted C₆₋₁₂ cycloalkylalkyl,C₃₋₁₂ cycloalkyl, substituted C₃₋₁₂ cycloalkyl, C₆₋₁₂ aryl, andsubstituted C₆₋₁₂ aryl. Such compounds can be referred to as prepolymersor adducts. Suitable polythioethers are disclosed, for example, in U.S.Pat. No. 6,172,179, which is incorporated by reference in its entirety.

A “polyalkoxysilyl group” refers to a group having the structure ofFormula (1):

—Si(—R⁷)_(x)(—OR⁷)_(3-x)  (1)

where x can be selected from 0, 1, and 2; and each R⁷ can independentlybe selected from C₁₋₄ alkyl. In a polyalkoxysilyl group, x can be 0, xcan be 1, or x can be 2. In a polyalkoxysilyl group, each R⁷ can beindependently selected from ethyl and methyl. Examples ofpolyalkoxysilyl groups, each R⁷ can be ethyl, or each R⁷ can be methyl.In a polyalkoxysilyl groups include —Si(—OCH₂CH₃)₃, —Si(—OCH₃)₃,—Si(—CH₃)(—OCH₃)₂, —Si(—CH₃)₂(—OCH₃), —Si(—CH₃)(—OCH₂CH₃)₂,—Si(—CH₃)₂(—OCH₂CH₃), —Si(—CH₂CH₃)(—OCH₃)₂, and —Si(—CH₂CH₃)₂(—OCH₃).

A “polyalkoxysilane” refers to a compound comprising a polyalkoxysilylgroup. A polyalkoxysilane can have the formula R¹¹—P—R¹² where P is thecore of the polyalkoxysilane, R¹¹ comprises a polyalkoxysilyl group, andR¹² comprises a reactive functional group.

“Substituted” refers to a group in which one or more hydrogen atoms areeach independently replaced with the same or different substituent(s). Asubstituent can be selected from halogen, —S(O)₂OH, —S(O)₂, —SH, —SR,C₁₋₆ alkyl, —COOH, —NO₂, —NR₂ where each R can independently be selectedfrom hydrogen and C₁₋₃ alkyl, —CN, —C═O, C₁₋₆ alkyl, —CF₃, —OH, phenyl,C₂₋₆ heteroalkyl, C₅₋₆ heteroaryl, C₁₋₆ alkoxy, and —COR where R can beC₁₋₆ alkyl. A substituent can be selected from —OH, —NH₂, and C₁₋₃alkyl.

Cure-on-demand sealants containing moisture-curable urethane-containingprepolymers comprising urethane segments incorporated into the backboneof sulfur-containing prepolymers are disclosed. The cure-on-demandcompositions include a moisture-curable urethane-containing prepolymerand a controlled release cure catalyst.

Moisture-curable prepolymers provided by the present disclosurerepresent an improvement over previously disclosed moisture-curableurethane-containing prepolymers such as those disclosed in U.S.Application Publication No. 2015/0252232, which is incorporated byreference in its entirety. Cured sealants prepared from moisture-curableurethane-prepolymers provided by the present disclosure exhibit enhancedtensile strength and elongation compared to the sealant compositionsdisclosed in U.S. Application Publication No. 2015/0252232. The enhancedtensile strength is believed to be imparted by the incorporation ofurethane segments into the polymer backbone.

Moisture curable urethane-containing prepolymers can comprise aurethane-containing prepolymer capped with polyalkoxysilyl groups.

A moisture-curable urethane-containing prepolymer can comprise amoisture-curable urethane-containing prepolymer of Formula (2a), amoisture-curable urethane-containing prepolymer of Formula (2b), or acombination thereof:

R³⁰—C(═O)—NH—R²⁰—NH—C(═O)—[—R⁶⁰—C(═O)—NH—R²⁰—NH—C(═O)—]_(w)—R⁶⁰—C(═O)—NH—R²⁰—NH—C(═O)—R³⁰  (2a)

B[—V′—S—R⁵⁰—S—(CH₂)₂—O—R¹³—O—[—C(═O)—NH—R²⁰—NH—C(═O)—R⁶⁰—]_(w)—C(═O)—NH—R²⁰—NH—C(═O)—R³⁰]_(z)  (2b)

wherein,

-   -   w is an integer from 1 to 100;    -   each R¹³ independently comprises C₂₋₁₀ alkanediyl;    -   each R²⁰ independently comprises a core of a diisocyanate;    -   each R³⁰ independently is a moiety comprising at least one        terminal polyalkoxysilyl group;    -   each R⁵⁰ independently comprises a core of a sulfur-containing        prepolymer;    -   each R⁶⁰ independently comprises a moiety having the structure        of Formula (3):

—O—R¹³—O—(CH₂)₂—S—R⁵⁰—S—(CH₂)₂—O—R¹³—O—  (3)

-   -   B represents a core of a z-valent, polyfunctionalizing agent        B(—V)_(z) wherein,        -   z is an integer from 3 to 6; and        -   each V is a moiety comprising a terminal group reactive with            a thiol group; and        -   each —V′— is derived from the reaction of —V with a thiol.

In prepolymers of Formula (2a) and Formula (2b), w can be an integerfrom 1 to 50, from 1 to 25, from 5 to 100, from 5 to 50, from 10 to 100,or from 10 to 50.

In prepolymers of Formula (2a) and Formula (2b), each R¹³ canindependently be ethane-diyl, n-propane-diyl, n-butane-diyl,n-pentane-diyl, or n-hexane-diyl. In prepolymers of Formula (2a) andFormula (2b), each R¹³ can independently be C₂₋₆ alkanediyl, C₂₋₄alkanediyl, or C₃₋₆ alkanediyl.

In prepolymers of Formula (2a) and Formula (2b), each R²⁰ canindependently be derived from a diisocyanate selected from acycloaliphatic diisocyanate such as, for example,4,4′-methylenedicyclohexyl diisocyanate.

In prepolymers of Formula (2a) and Formula (2b), each R³⁰ can comprise aterminal polyalkoxysilyl group having the structure of Formula (1):

—Si(—R⁷)_(x)(—OR⁷)_(3-x)  (1)

where x is selected from 0, 1, and 2; and each R⁷ is independentlyselected from C₁₋₄ alkyl.

In prepolymers of Formula (2a) and Formula (2b), each R³⁰ canindependently comprise a moiety having the structure of Formula (4a),Formula (4b), or a combination thereof:

—NH(—R⁹—Si(—R⁷)_(x)(—OR⁷)_(3-x))  (4a)

—N(—R⁹—Si(—R⁷)_(x)(—OR⁷)_(3-x))₂  (4b)

where x can be selected from 0, 1, and 2; each R⁷ can independently beselected from C₁₋₄ alkyl; and each R⁹ can independently be C₁₋₁₀alkanediyl. In moieties of Formula (4a) and Formula (4b), each R⁹ can beC₁₋₆ alkanediyl, C₁₋₄ alkanediyl, C₂₋₆ alkanediyl, ethane-diyl,n-propane-diyl, n-butane-diyl, n-pentane-diyl, or n-hexane-diyl.

In prepolymers of Formula (2a) and Formula (2b), each R³⁰ can have thestructure of Formula (4c):

—NH—(CH₂)₃—Si(—OCH₃)₃  (4c)

In prepolymers of Formula (2a) and Formula (2b), each R³⁰ canindependently be derived from an aminosilane.

In prepolymers of Formula (2a) and Formula (2b), each R⁵⁰ can comprise acore of a thiol-terminated sulfur-containing prepolymer such as, forexample, a thiol-terminated polythioether, a thiol-terminatedpolysulfide, a thiol-terminated sulfur-containing polyformal, or acombination of any of the foregoing.

In prepolymers of Formula (2a) and Formula (2b), each R⁵⁰ can be derivedfrom a polythioether prepolymer and can have the structure of Formula(5):

—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—  (5)

wherein,

-   -   each R¹ independently is selected from C₂₋₁₀ alkanediyl, C₆₋₈        cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, C₅₋₈        heterocycloalkanediyl, and —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—,        wherein,        -   p is an integer from 2 to 6;        -   q is an integer from 1 to 5;        -   r is an integer from 2 to 10;        -   each R³ is independently selected from hydrogen and methyl;            and        -   each X is independently selected from —O—, —S—, and —NR—,            wherein R is selected from hydrogen and methyl;    -   each R² is independently selected from C₁₋₁₀ alkanediyl, C₆₋₈        cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, and        —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—, wherein p, q, r, R³, and X        are as defined as for R¹;    -   m is an integer from 0 to 50;    -   n is an integer from 1 to 60; and    -   s is an integer from 2 to 6.

The isocyanate content of a moisture-curable urethane-containingprepolymer can be, for example, from 1% to 10%, from 2% to 6%, or from3% to 5%.

It can be appreciated that moisture-curable urethane-containingprepolymers provided by the present disclosure may be synthesized by anumber of routes. The functional groups of the precursors can be adaptedand selected for a particular reaction chemistry. For example, it can beconvenient that the sulfur-containing prepolymer comprise thiol orhydroxyl functional groups. In embodiments in which thesulfur-containing prepolymer has functional hydroxyl groups, adiisocyanate may be directly reacted with the sulfur-containingprepolymer. In embodiments in which the precursor sulfur-containingprepolymer is thiol-terminated, the thiol groups may be capped with ahydroxyl functional moiety to provide a hydroxyl-terminatedsulfur-containing adduct that may then be reacted with a diisocyanate.The diisocyanate-terminated adduct may then be reacted with a compoundcomprising a group reactive with an isocyanate group, and a terminalpolyalkoxysilyl group.

A moisture-curable urethane-containing prepolymer can be derived fromthe reaction of a thiol-terminated sulfur-containing prepolymer, ahydroxy vinyl ether, a diisocyanate, and an aminosilane, and optionallya polyfunctionalizing agent.

Moisture-curable urethane-containing prepolymers provided by the presentdisclosure can comprise the reaction product of reactants comprising anisocyanate-terminated urethane-containing adduct, and an aminosilane.Moisture-curable urethane-containing prepolymers provided by the presentdisclosure can comprise the reaction product of reactants comprising anisocyanate-terminated urethane-containing adduct, and a compoundcomprising a group reactive with an isocyanate and at least onepolyalkoxysilyl group.

A general reaction sequence for preparing moisture-curableurethane-containing prepolymers is summarized in FIG. 1. As shown inFIG. 1, a sulfur-containing polythiol (A) such as a sulfur-containingdithiol, a sulfur-containing trithiol, or combination thereof, can bereacted with a hydroxy vinyl ether (B) to provide a hydroxyl-terminatedsulfur-containing adduct (C). The hydroxyl-terminated sulfur-containingadduct (C) can then be reacted with a diisocyanate (D) to provide anisocyanate-terminated urethane-containing adduct (E) in which urethanesegments derived from the diisocyanate are incorporated into thebackbone of the sulfur-containing prepolymer. The isocyanate-terminatedurethane-containing adduct (E) is then reacted with a compound (F)comprising a group reactive with an isocyanate group and at least onepolyalkoxysilyl group such as an aminosilane to provide amoisture-curable urethane-containing prepolymer (G).

Sulfur-containing prepolymers useful in preparing moisture-curableurethane-containing prepolymers include polythioethers, polysulfides,sulfur-containing polyformals, and combinations of any of the foregoing.A sulfur-containing prepolymer may be difunctional, or may have afunctionality greater than 2 such as 3, 4, 5, or 6. A sulfur-containingprepolymer may comprise a mixture of sulfur-containing prepolymershaving different functionalities characterized by an averagefunctionality from 2.05 to 6, from 2.1 to 4, from 2.1 to 3, from 2.2 to2.8, or from 2.4 to 2.6.

Examples of suitable polythioethers are disclosed, for example, in U.S.Pat. No. 6,172,179.

A sulfur-containing prepolymer can comprise a polythioether comprising abackbone comprising the structure of Formula (5a):

—R¹—[—S—(CH₂)₂—O—[—R²—O—]_(m)—(CH₂)₂—S—R¹]_(n)—  (5a)

wherein:

-   -   each R¹ is independently selected from a C₂₋₁₀ n-alkanediyl        group, a C₃₋₆ branched alkanediyl group, a C₆₋₈ cycloalkanediyl        group, a C₆₋₁₀ alkanecycloalkanediyl group, a heterocyclic        group, a —[(—CHR³—)_(p)—X—]_(q)—(CHR³)_(r)— group, wherein each        R³ is selected from hydrogen and methyl;    -   each R² is independently selected from a C₂₋₁₀ n-alkanediyl        group, a C₃₋₆ branched alkanediyl group, a C₆₋₈ cycloalkanediyl        group, a C₆₋₁₄ alkanecycloalkanediyl group, a heterocyclic        group, and a —[(—CH₂—)_(p)—X—]_(q)—(CH₂)_(r)— group;    -   each X is independently selected from O, S, and a —NR— group, in        which R is selected from hydrogen and a methyl group;    -   m ranges from 0 to 50;    -   n is an integer ranging from 1 to 60;    -   p is an integer ranging from 2 to 6;    -   q is an integer ranging from 1 to 5; and r is an integer ranging        from 2 to 10.

In moieties of Formula (5) and Formula (5a), R¹ can be—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)— wherein each X can independently beselected from —O— and —S—. In moieties where R¹ can be—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—, each X can be —O— or each X can be—S—.

In moieties of Formula (5) and Formula (5a), R¹ can be—[—(CH₂)_(p)—X—]_(q)—(CH₂)_(r)— where each X can independently beselected from —O— and —S—. In moieties where R¹ is—[—(CH₂)_(p)—X—]_(q)—(CH₂)_(r)—, each X can be —O— or each X is —S—.

In moieties of Formula (5) and Formula (5a), R¹ can be—[(—CH₂—)_(p)—X—]_(q)—(CH₂)_(r)—, where p can be 2, X can be O, q can be2, r can be 2, R² can be ethanediyl, m can be 2, and n can be 9.

In moieties of Formula (5) and Formula (5a), each R¹ can be derived fromdimercaptodioxaoctane (DMDO) or each R¹ can be derived fromdimercaptodiethylsulfide (DMDS).

In moieties of Formula (5) and Formula (5a), each m can independently bean integer from 1 to 3. In moieties of Formula (5) and Formula (5a),each m can be the same and can be 1, 2, or 3.

In moieties of Formula (5) and Formula (5a), n can be an integer from 1to 30, an integer from 1 to 20, an integer from 1 to 10, or and aninteger from 1 to 5. In addition, n may be any integer from 1 to 60.

In moieties of Formula (5) and Formula (5a), each p can independently beselected from 2, 3, 4, 5, and 6. In moieties of Formula (5) and Formula(5a), each p can be the same and is 2, 3, 4, 5, or 6.

A sulfur-containing prepolymer can be a polysulfide. Polysulfides referto prepolymers that contain one or more sulfide linkages, i.e., —S_(x)—linkages, where x is from 2 to 4, in the polymer backbone and/or inpendant positions on the polymer chain. A polysulfide polymer can havetwo or more sulfur-sulfur linkages. Suitable polysulfides arecommercially available, for example, from Akzo Nobel and Toray FineChemicals under the names Thiokol-LP and Thioplast®. Thioplast® productsare available in a wide range of molecular weights ranging, for example,from less than 1,100 Daltons to over 8,000 Daltons, with molecularweight being the average molecular weight in grams per mole. In somecases, the polysulfide has a number average molecular weight of 1,000Daltons to 4,000 Daltons. Examples of suitable polysulfides aredisclosed, for example, in U.S. Pat. No. 4,623,711.

Sulfur-containing polyformal prepolymers useful in aerospace sealantapplications are disclosed, for example, in U.S. Application PublicationNo. 2012/0234205 and in U.S. Application Publication No. 2012/0238707,each of which is incorporated by reference in its entirety.

A sulfur-containing prepolymer can comprise a metal ligand-containingsulfur-containing prepolymer in which a metal ligand is incorporatedinto the backbone of the prepolymer. Metal-ligand containingsulfur-containing prepolymers are disclosed, for example, in U.S.Application Publication No. 2014/0275474, which is incorporated byreference in its entirety.

A sulfur-containing prepolymer may be difunctional, or may have afunctionality greater than 2 such as 3, 4, 5, or 6. A sulfur-containingprepolymer may comprise a mixture of sulfur-containing prepolymer havingdifferent functionalities characterized by an average functionality, forexample, from 2.05 to 6, from 2.1 to 4, from 2.1 to 3, from 2.2 to 2.8,or from 2.4 to 2.6.

A sulfur-containing prepolymer can comprise urethane segmentsincorporated into the backbone of the prepolymer. Urethane-containingprepolymers are disclosed in U.S. Application Publication No.2015/0252230.

A thiol-terminated sulfur-containing prepolymer can comprise athiol-terminated polythioether, a thiol-terminated polysulfide, athiol-terminated sulfur-containing polyformal, or a combination of anyof the foregoing.

A thiol-terminated sulfur-containing prepolymer can comprise athiol-terminated polythioether of Formula (6a), a thiol-terminatedpolythioether of Formula (6b), or a combination thereof:

HS—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—SH  (6a)

{HS—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—S—V′—}_(z)B  (6b)

wherein:

-   -   each R¹ independently is selected from C₂₋₁₀ alkanediyl, C₆₋₈        cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, C₅₋₈        heterocycloalkanediyl, and —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—,        wherein:        -   p is an integer from 2 to 6;        -   q is an integer from 1 to 5;        -   r is an integer from 2 to 10;        -   each R³ is independently selected from hydrogen and methyl;            and        -   each X is independently selected from —O—, —S—, and —NR—,            wherein R is selected from hydrogen and methyl;    -   each R² is independently selected from C₁₋₁₀ alkanediyl, C₆₋₈        cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, and        —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—, wherein p, q, r, R³, and X        are as defined as for R¹;    -   m is an integer from 0 to 50;    -   n is an integer from 1 to 60;    -   s is an integer from 2 to 6;    -   B represents a core of a z-valent, vinyl-terminated        polyfunctionalizing agent B(—V)_(z) wherein:        -   z is an integer from 3 to 6; and        -   each V is a group comprising a terminal vinyl group; and    -   each —V′— is derived from the reaction of —V with a thiol.

In prepolymers of Formula (6a) and in Formula (6b), R¹ can be—[(—CH₂—)_(p)—X—]_(q)—(CH₂)_(r)—, where p can be 2, X can be —O—, q canbe 2, r can be 2, R² can be ethanediyl, m can be 2, and n can be 9.

In prepolymers of Formula (6a) and Formula (6b), R¹ can be selected fromC₂₋₆ alkanediyl and —[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—.

In prepolymers of Formula (6a) and Formula (6b), R¹ can be—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—, and X can be —O— or X can be —S—.

In prepolymers of Formula (6a) and Formula (6b), where R¹ is—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—, p can be 2, r can be 2, q can be 1,and X can be —S—; or p can be 2, q can be 2, r can be 2, and X can be—O—; or p can be 2, r can be 2, q can be 1, and X can be —O—.

In prepolymers of Formula (6a) and Formula (6b), where R¹ is—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—, each R³ can be hydrogen, or at leastone R³ can be methyl.

In prepolymers of Formula (6a) and Formula (6b), each R¹ can be thesame, or at least one R¹ is different.

Various methods can be used to prepare thiol-terminated polythioethersof Formula (6a) and Formula (6b). Examples of suitable thiol-terminatedpolythioethers, and methods for their production, are described in U.S.Pat. No. 6,172,179. Such thiol-terminated polythioethers may bedifunctional, that is, linear polymers having two terminal thiol groups,or polyfunctional, that is, branched polymers having three or moreterminal thiol groups. Suitable thiol-terminated polythioethers arecommercially available, for example, as Permapol® P3.1E, from PRC-DeSotoInternational Inc., Sylmar, Calif.

A thiol-terminated sulfur-containing prepolymer can comprise apolythioether. A sulfur-containing prepolymer may comprise a mixture ofdifferent thiol-terminated polythioethers and the thiol-terminatedpolythioethers may have the same or different functionality. Asulfur-containing prepolymer can have an average functionality from 2 to6, from 2 to 4, from 2 to 3, or from 2.05 to 2.5. For example, asulfur-containing prepolymer can be selected from a difunctionalsulfur-containing polymer, a trifunctional sulfur-containing prepolymer,and a combination thereof.

A thiol-terminated polythioether can be prepared by reacting a polythioland a diene such as a divinyl ether, and the respective amounts of thereactants used to prepare the thiol-terminated polythioethers can bechosen to yield terminal thiol groups. Thus, in some cases, (n or >n,such as n+1) moles of a polythiol, such as a dithiol or a mixture of atleast two different dithiols and 0.05 moles to 1 moles, such as 0.1moles to 0.8 moles, of a thiol-terminated polyfunctionalizing agent maybe reacted with (n) moles of a diene, such as a divinyl ether, or amixture of at least two different dienes such as a divinyl ether. Athiol-terminated polyfunctionalizing agent can be present in thereaction mixture in an amount sufficient to provide a thiol-terminatedpolythioether having an average functionality of from 2.05 to 3, such as2.1 to 2.8.

The reaction used to make a thiol-terminated polythioether may becatalyzed by a free radical catalyst. Suitable free radical catalystsinclude azo compounds, for example azobisnitrile compounds such asazo(bis)isobutyronitrile (AIBN); organic peroxides, such as benzoylperoxide and t-butyl peroxide; and inorganic peroxides, such as hydrogenperoxide. The reaction can also be effected by irradiation withultraviolet light either with or without a radicalinitiator/photosensitizer. Ionic catalysis methods, using eitherinorganic or organic bases, e.g., triethylamine, may also be used.

Suitable thiol-terminated polythioethers may be produced by reacting adivinyl ether or mixtures of divinyl ethers with an excess of a dithiolor a mixtures of dithiols.

Thus, a thiol-terminated polythioether can comprise the reaction productof reactants comprising:

(a) a dithiol of Formula (7):

HS—R¹—SH  (7)

-   -   wherein:        -   R¹ is selected from C₂₋₆ alkanediyl, C₆₋₈ cycloalkanediyl,            C₆₋₁₀ alkanecycloalkanediyl, C₅₋₈ heterocycloalkanediyl, and            —[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—; wherein:        -   each R³ is independently selected from hydrogen and methyl;        -   each X is independently selected from —O—, —S—, —NH—, and            —NR— wherein R is selected from hydrogen and methyl;        -   p is an integer from 2 to 6;        -   q is an integer from 1 to 5; and        -   r is an integer from 2 to 10; and        -   (b) a divinyl ether of Formula (8):

CH₂═CH—O—(—R²—O—)_(m)—CH═CH₂  (8)

-   -   wherein:        -   each R² is independently selected from C₁₋₁₀ alkanediyl,            C₆₋₈ cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, and            —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—, wherein p, q, r, R³,            and X are as defined above; and        -   m is an integer from 0 to 50.            The reactants may further comprise (c) a polyfunctional            compound such as a polyfunctional compound B(—V)_(z), where            B, —V, and z are as defined herein.

Dithiols suitable for use in preparing thiol-terminated polythioethersinclude those having a structure of Formula (7), other dithiolsdisclosed herein, or combinations of any of the dithiols disclosedherein. A dithiol can have the structure of Formula (7):

HS—R¹—SH  (7)

wherein:

-   -   R¹ is selected from C₂₋₆ alkanediyl, C₆₋₈ cycloalkanediyl, C₆₋₁₀        alkanecycloalkanediyl, C₅₋₈ heterocycloalkanediyl, and        —[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—;    -   wherein:        -   each R³ is independently selected from hydrogen and methyl;        -   each X is independently selected from —O—, —S—, and —NR—            wherein R is selected from hydrogen and methyl;        -   p is an integer from 2 to 6;        -   q is an integer from 1 to 5; and        -   r is an integer from 2 to 10.

In a dithiol of Formula (7), R¹ can be—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—.

In a dithiol of Formula (7), X can be selected from —O— and —S—, andthus —[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)— in Formula (7) can be—[(—CHR³—)_(p)—O—]_(q)—(CHR³)_(r)— or—[(—CHR³—)_(p)—S—]_(q)—(CHR³)_(r)—. In a dithiol of Formula (7), p and rcan be equal, such as where p and r are both two.

In a dithiol of Formula (7), R¹ can be selected from C₂₋₆ alkanediyl and—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—.

In a dithiol of Formula (7), R¹ can be—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—, X can be —O— or X can be —S—.

In a dithiol of Formula (7) where R¹ can be—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—, p can be 2, r can be 2, q can be 1,and X can be —S—; or p can be 2, q can be 2, r can be 2, and X can be—O—; or p can be 2, r can be 2, q can be 1, and X can be —O—.

In a dithiol of Formula (7), where R¹ is—[—(CHR³)_(p)—X—]_(q)—(CHR³)_(r)—, each R³ can be hydrogen, or at leastone R³ can be methyl.

Examples of suitable dithiols include, for example, 1,2-ethanedithiol,1,2-propanedithiol, 1,3-propanedithiol, 1,3-butanedithiol,1,4-butanedithiol, 2,3-butanedithiol, 1,3-pentanedithiol,1,5-pentanedithiol, 1,6-hexanedithiol, 1,3-dimercapto-3-methylbutane,dipentenedimercaptan, ethylcyclohexyldithiol (ECHDT),dimercaptodiethylsulfide, methyl-substituted dimercaptodiethylsulfide,dimethyl-substituted dimercaptodiethylsulfide, dimercaptodioxaoctane,1,5-dimercapto-3-oxapentane, and a combination of any of the foregoing.A polythiol may have one or more pendent groups selected from a lower(e.g., C₁₋₆) alkyl group, a lower alkoxy group, and a hydroxyl group.Suitable alkyl pendent groups include, for example, C₁₋₆ linear alkyl,C₃₋₆ branched alkyl, cyclopentyl, and cyclohexyl.

Other examples of suitable dithiols include dimercaptodiethylsulfide(DMDS) (in Formula (7), R¹ is —[(—CH₂—)_(p)—X—]_(q)—(CH₂)_(r)—, whereinp is 2, r is 2, q is 1, and X is —S—); dimercaptodioxaoctane (DMDO) (inFormula (7), R¹ is —[(—CH₂—)_(p)—X—]_(q)—(CH₂)_(r)—, wherein p is 2, qis 2, r is 2, and X is —O—); and 1,5-dimercapto-3-oxapentane (in Formula(7), R¹ is —[(—CH₂—)_(p)—X—]_(q)—(CH₂)_(r)—, wherein p is 2, r is 2, qis 1, and X is —O—). It is also possible to use dithiols that includeboth heteroatoms in the carbon backbone and pendent alkyl groups, suchas methyl groups. Such compounds include, for example,methyl-substituted DMDS, such as HS—CH₂CH(—CH₃)—S—CH₂CH₂—SH,HS—CH(—CH₃)CH₂—S—CH₂CH₂—SH and dimethyl substituted DMDS, such asHS—CH₂CH(—CH₃)—S—CH(—CH₃)CH₂—SH and HS—CH(—CH₃)CH₂—S—CH₂CH(—CH₃)—SH.

Suitable divinyl ethers for preparing polythioethers include, forexample, divinyl ethers of Formula (8):

CH₂═CH—O—(—R²—O—)_(m)—CH═CH₂  (8)

where R² in Formula (8) is selected from a C₂₋₆ n-alkanediyl group, aC₃₋₆ branched alkanediyl group, a C₆₋₈ cycloalkanediyl group, a C₆₋₁₀alkanecycloalkanediyl group, and —[(—CH₂—)_(p)—O—]_(q)—(—CH₂—)_(r)—,where p is an integer ranging from 2 to 6, q is an integer from 1 to 5,and r is an integer from 2 to 10. In a divinyl ether of Formula (8), R²can be a C₂₋₆ n-alkanediyl group, a C₃₋₆ branched alkanediyl group, aC₆₋₈ cycloalkanediyl group, a C₆₋₁₀ alkanecycloalkanediyl group, or—[(—CH₂—)_(p)—O—]_(q)—(—CH₂—)_(r)—.

Suitable divinyl ethers include, for example, compounds having at leastone oxyalkanediyl group, such as from 1 to 4 oxyalkanediyl groups, i.e.,compounds in which m in Formula (8) is an integer ranging from 1 to 4.In a divinyl ether, m in Formula (8) can be an integer ranging from 2 to4. It is also possible to employ commercially available divinyl ethermixtures that are characterized by a non-integral average value for thenumber of oxyalkanediyl units per molecule. Thus, m in Formula (8) canalso take on rational number values ranging from 0 to 10.0, such as from1.0 to 10.0, from 1.0 to 4.0, or from 2.0 to 4.0.

Examples of suitable vinyl ethers include, divinyl ether, ethyleneglycol divinyl ether (EG-DVE) (R² in Formula (8) is ethanediyl and m is1), butanediol divinyl ether (BD-DVE) (R² in Formula (8) is butanediyland m is 1), hexanediol divinyl ether (HD-DVE) (R² in Formula (8) ishexanediyl and m is 1), diethylene glycol divinyl ether (DEG-DVE) (R² inFormula (8) is ethanediyl and m is 2), triethylene glycol divinyl ether(R² in Formula (8) is ethanediyl and m is 3), tetraethylene glycoldivinyl ether (R² in Formula (8) is ethanediyl and m is 4),cyclohexanedimethanol divinyl ether, polytetrahydrofuryl divinyl ether;trivinyl ether monomers, such as trimethylolpropane trivinyl ether;tetrafunctional ether monomers, such as pentaerythritol tetravinylether; and combinations of two or more such polyvinyl ether monomers. Apolyvinyl ether may have one or more pendant groups selected from alkylgroups, hydroxyl groups, alkoxy groups, and amine groups.

In divinyl ethers in which R² in Formula (8) is C₃₋₆ branched alkanediylmay be prepared by reacting a polyhydroxyl compound with acetylene.Examples of divinyl ethers of this type include compounds in which R² inFormula (8) is an alkyl-substituted methanediyl group such as—CH(—CH₃)—, for which R² in Formula (8) is ethanediyl and m is 3.8, oran alkyl-substituted ethanediyl.

Other useful divinyl ethers include compounds in which R² in Formula (8)is polytetrahydrofuryl (poly-THF) or polyoxyalkanediyl, such as thosehaving an average of 3 monomer units.

Two or more types of polyvinyl ether monomers of Formula (8) may beused. Thus, two dithiols of Formula (7) and one polyvinyl ether monomerof Formula (8), one dithiol of Formula (7) and two polyvinyl ethermonomers of Formula (8), two dithiols of Formula (7) and two divinylether monomers of Formula (8), and more than two compounds of one orboth Formula (7) and Formula (8), may be used to produce a variety ofthiol-terminated polythioethers.

A polyvinyl ether monomer can comprise 20 mole percent to less than 50mole percent of the reactants used to prepare a thiol-terminatedpolythioether, or 30 mole percent to less than 50 mole percent.

Relative amounts of dithiols and divinyl ethers can be selected to yieldpolythioethers having terminal thiol groups. Thus, a dithiol of Formula(7) or a mixture of at least two different dithiols of Formula (7), canbe reacted with of a divinyl ether of Formula (8) or a mixture of atleast two different divinyl ethers of Formula (8) in relative amountssuch that the molar ratio of thiol groups to vinyl groups is greaterthan 1:1, such as 1.1 to 2.0:1.0.

The reaction between dithiols and divinyl ethers and/or polythiols andpolyvinyl ethers may be catalyzed by a free radical catalyst. Suitablefree radical catalysts include, for example, azo compounds, for exampleazobisnitriles such as azo(bis)isobutyronitrile (AIBN); organicperoxides such as benzoyl peroxide and t-butyl peroxide; and inorganicperoxides such as hydrogen peroxide. The catalyst may be a free-radicalcatalyst, an ionic catalyst, or ultraviolet radiation. A catalyst maynot comprise acidic or basic compounds, and may not produce acidic orbasic compounds upon decomposition. Examples of free-radical catalystsinclude azo-type catalyst, such as Vazo®-57 (Du Pont), Vazo®-64 (DuPont), Vazo®-67 (Du Pont), Vazo®-70 (Wako Specialty Chemicals), andVazo®-65B (Wako Specialty Chemicals). Examples of other free-radicalcatalysts are alkyl peroxides, such as t-butyl peroxide. The reactionmay also be effected by irradiation with ultraviolet light either withor without a cationic photoinitiating moiety.

Thiol-terminated polythioethers provided by the present disclosure maybe prepared by combining at least one compound of Formula (7) and atleast one compound of Formula (8) followed by addition of an appropriatecatalyst, and carrying out the reaction at a temperature from 30° C. to120° C., such as 70° C. to 90° C., for a time from 2 hours to 24 hours,such as 2 hours to 6 hours.

Thiol-terminated polythioethers may comprise a polyfunctionalpolythioether, i.e., may have an average functionality of greater than2.0. Suitable polyfunctional thiol-terminated polythioethers include,for example, those having the structure of Formula (6b):

{HS—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—S—V′—}_(z)B  (6b)

wherein Z has a value from 3 to 6, such as 3, 4, 5, or 6. Athiol-terminated polythioether of Formula (6b) can be a mixture ofpolyfunctional thiol-terminated polythioethers of Formula (6b) wherein zhas an average value of greater than 3.0, a value between 3 and 4, avalue between 3 and 5, a value between 3 and 6, or can be an integerfrom 3 to 6.

Polyfunctionalizing agents suitable for use in preparing suchpolyfunctional thiol-terminated prepolymers include trifunctionalizingagents, that is, compounds where z is 3. Suitable trifunctionalizingagents include, for example, triallyl cyanurate (TAC),1,2,3-propanetrithiol, isocyanurate-containing trithiols, andcombinations thereof, as disclosed in U.S. Application Publication No.2010/0010133 at paragraphs [0102]-[0105], which is incorporated byreference in its entirety, and isocyanurates as disclosed, for example,in U.S. Application Publication No. 2011/0319559, which is incorporatedby reference in its entirety. Other useful polyfunctionalizing agentsinclude trimethylolpropane trivinyl ether, and the polythiols describedin U.S. Pat. Nos. 4,366,307; 4,609,762; and 5,225,472, each of which isincorporated by reference in its entirety. Mixtures ofpolyfunctionalizing agents may also be used. As a result,bis(sulfonyl)alkanol-containing polythioethers provided by the presentdisclosure may have a wide range of average functionality. For example,when combined with difunctional prepolymers, trifunctionalizing agentsmay afford average functionalities from 2.05 to 3.0, such as from 2.1 to2.6. Wider ranges of average functionality may be achieved by usingtetrafunctional or higher functionality polyfunctionalizing agents.Functionality may also be determined by factors such as stoichiometry,as will be understood by those skilled in the art.

A hydroxyl-terminated sulfur-containing adduct may be formed by reactinga thiol-terminated sulfur-containing prepolymer with a hydroxyl vinylether.

Hydroxyl vinyl ethers can be used to functionalize a thiol-terminatedsulfur-containing prepolymer with a group reactive with an isocyanategroup. A hydroxyl-functional vinyl ether can have the structure ofFormula (9):

CH₂═CH—O—(CH₂)_(t)—OH  (9)

where t is an integer from 2 to 10. In hydroxyl-functional vinyl ethersof Formula (9), t can be 1, 2, 3, 4, 5, or t can be 6.

Examples of suitable hydroxyl-functional vinyl ethers useful forreacting with thiol-terminated sulfur-containing prepolymers include1,4-cyclohexane dimethylol monovinyl ether, 1-methyl-3-hydroxypropylvinyl ether, 4-hydroxybutyl vinyl ether, and a combination of any of theforegoing. A hydroxyl-functional vinyl ether can be 4-hydroxybutyl vinylether.

Hydroxyl-terminated sulfur-containing adducts provided by the presentdisclosure can comprise terminal hydroxyl groups that are reactive withisocyanate groups and may be reacted directly with a polyisocyanate suchas a diisocyanate to provide isocyanate-terminated urethane-containingadducts useful in forming moisture-curable prepolymers provided by thepresent disclosure.

A sulfur-containing prepolymer may be functionalized to provide groupssufficiently reactive with isocyanate groups. For example,thiol-terminated sulfur-containing prepolymers provide suitableprecursors to form moisture-curable prepolymers of the presentdisclosure. To render a thiol-terminated sulfur-containing prepolymerreactive with isocyanate groups the thiol-terminated sulfur-containingprepolymer may be functionalized with hydroxyl groups. Athiol-terminated sulfur-containing prepolymer can be reacted with acompound having a group reactive with an alkenyl group and a hydroxylgroup to provide a hydroxyl-terminated sulfur-containing adduct.Examples of such compounds include hydroxy vinyl ethers.

A hydroxyl-terminated sulfur-containing adduct can comprise ahydroxyl-terminated polythioether adduct, such as a hydroxyl-terminatedpolythioether adduct of Formula (10a), a hydroxyl-terminatedpolythioether adduct of Formula (10b), or a combination thereof:

R⁶—S—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—S—R⁶  (10a)

{R⁶—S—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—S—V′—}_(z)B  (10b)

where R¹, R², m, n, and s are defined herein, and each R⁶ can be amoiety comprising a terminal hydroxyl group.

In adducts of Formula (10a) and Formula (10b), each R⁶ can be derivedfrom a hydroxy vinyl ether and can have the structure of Formula (11):

—CH₂—CH₂—O—R¹³—OH  (11)

where R¹³ can be C₂₋₁₀ alkanediyl or R¹³ can be —(CH₂)₄— or —(CH₂)₃—.

A hydroxyl-terminated sulfur-containing adduct can comprise the reactionproduct of a difunctional thiol-terminated polythioether, atrifunctional thiol-terminated polythioether, or a combination thereof;and a hydroxy vinyl ether. A hydroxyl-terminated sulfur-containingadduct can comprise the reaction product of Permapol® 3.1E and ahydroxyvinyl ether, such as 4-hydroxybutyl vinyl ether.

An isocyanate-terminated urethane-containing adduct can comprise anisocyanate-terminated urethane-containing polythioether adduct, anisocyanate-terminated urethane-containing polysulfide adduct, anisocyanate-terminated urethane-containing sulfur-containing polyformaladduct, or a combination of any of the foregoing.

Isocyanate-terminated urethane-containing adducts may comprise thereaction product of reactants comprising a hydroxyl-terminatedsulfur-containing adduct and a diisocyanate. The ratio ofhydroxyl-terminated sulfur-containing adduct and diisocyanate can beselected such that the diisocyanate is incorporated into the backbone ofthe sulfur-containing prepolymer and terminates the prepolymer. Anisocyanate content of an isocyanate-terminated urethane-containingprepolymer can be from 1% to 10%, from 2% to 6%, or from 3% to 5%.

Isocyanate-terminated urethane-containing adducts can be prepared byreacting a polyisocyanate with a sulfur-containing adduct comprisingterminal groups reactive with isocyanate groups such as terminalhydroxyl groups. A polyisocyanate can be difunctional, n-functionalwhere n is an integer from 3 to 6, or a combination of any of theforegoing. A polyisocyanate can be difunctional and can be referred toas a diisocyanate. A diisocyanate may be aliphatic, alicyclic oraromatic.

Examples of suitable aliphatic diisocyanates include, 1,6-hexamethylenediisocyanate, 1,5-diisocyanato-2-methylpentane,methyl-2,6-diisocyanatohexanoate, bis(isocyanatomethyl)cyclohexane,1,3-bis(isocyanatomethyl)cyclohexane, 2,2,4-trimethylhexane1,6-diisocyanate, 2,4,4-trimethylhexane 1,6-diisocyanate,2,5(6)-bis(isocyanatomethyl)cyclo[2.2.1]heptane,1,3,3-trimethyl-1-(isocyanatomethyl)-5-isocyanatocyclohexane,1,8-diisocyanato-2,4-dimethyloctane,octahydro-4,7-methano-1H-indenedimethyl diisocyanate, and1,1′-methylenebis(4-isocyanatocyclohexane), and 4,4-methylenedicyclohexyl diisocyanate) (H₁₂MDI). Examples of suitable aromaticdiisocyanates include 1,3-phenylene diisocyanate, 1,4-phenylenediisocyanate, 2,6-toluene diisocyanate (2,6-TDI), 2,4-toluenediisocyanate (2,4-TDI), a blend of 2,4-TDI and 2,6-TDI,1,5-diisocyanatonaphthalene, diphenyl oxide 4,4′-diisocyanate,4,4′-methylenediphenyl diisocyanate (4,4-MDI), 2,4′-methylenediphenyldiisocyanate (2,4-MDI), 2,2′-diisocyanatodiphenylmethane (2,2-MDI),diphenylmethane diisocyanate (MDI), 3,3′-dimethyl-4,4′-biphenyleneisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate,1-[(2,4-diisocyanatophenyl)methyl]-3-isocyanato-2-methyl benzene, and2,4,6-triisopropyl-m-phenylene diisocyanate.

Examples of suitable alicyclic diisocyanates from which thediisocyanates may be selected include isophorone diisocyanate,cyclohexane diisocyanate, methylcyclohexane diisocyanate,bis(isocyanatomethyl)cyclohexane, bis(isocyanatocyclohexyl)methane,bis(isocyanatocyclohexyl)-2,2-propane,bis(isocyanatocyclohexyl)-1,2-ethane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane,and2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane.

Examples of suitable aromatic diisocyanates in which the isocyanategroups are not bonded directly to the aromatic ring include, but are notlimited to, bis(isocyanatoethyl)benzene, α,α,α′,α′-tetramethylxylenediisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene,bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene,bis(isocyanatomethyl)diphenyl ether, bis(isocyanatoethyl)phthalate, and2,5-di(isocyanatomethyl)furan. Aromatic diisocyanates having isocyanategroups bonded directly to the aromatic ring include phenylenediisocyanate, ethylphenylene diisocyanate, isopropylphenylenediisocyanate, dimethylphenylene diisocyanate, diethylphenylenediisocyanate, diisopropylphenylene diisocyanate, naphthalenediisocyanate, methylnaphthalene diisocyanate, biphenyl diisocyanate,4,4′-diphenylmethane diisocyanate,bis(3-methyl-4-isocyanatophenyl)methane, bis(isocyanatophenyl)ethylene,3,3′-dimethoxy-biphenyl-4,4′-diisocyanate, diphenylether diisocyanate,bis(isocyanatophenylether)ethyleneglycol,bis(isocyanatophenylether)-1,3-propyleneglycol, benzophenonediisocyanate, carbazole diisocyanate, ethylcarbazole diisocyanate,dichlorocarbazole diisocyanate, 4,4′-diphenylmethane diisocyanate,p-phenylene diisocyanate, 2,4-toluene diisocyanate, and 2,6-toluenediisocyanate.

Other examples of suitable diisocyanates include 1,3-phenylenediisocyanate, 1,4-phenylene diisocyanate, 2,6-toluene diisocyanate(2,6-TDI), 2,4-toluene diisocyanate (2,4-TDI), a blend of 2,4-TDI and2,6-TDI, 1,5-diisocyanato naphthalene, diphenyl oxide 4,4′-diisocyanate,4,4′-methylenediphenyl diisocyanate (4,4-MDI), 2,4′-methylenediphenyldiisocyanate (2,4-MDI), 2,2′-diisocyanatodiphenylmethane (2,2-MDI),diphenylmethane diisocyanate (MDI), 3,3′-dimethyl-4,4′-biphenyleneisocyanate, 3,3′-dimethoxy-4,4′-biphenylene diisocyanate,1-[(2,4-diisocyanatophenyl)methyl]-3-isocyanato-2-methyl benzene,2,4,6-triisopropyl-m-phenylene diisocyanate, 4,4-methylene dicyclohexyldiisocyanate (H₁₂MDI), and a combination of any of the foregoing.

Additional examples of suitable aromatic diisocyanates include1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate, 2,6-toluenediisocyanate (2,6-TDI), 2,4-toluene diisocyanate (2,4-TDI), a blend of2,4-TDI and 2,6-TDI, 1,5-diisocyanato naphthalene, diphenyl oxide4,4′-diisocyanate, 4,4′-methylenediphenyl diisocyanate (4,4-MDI),2,4′-methylenediphenyl diisocyanate (2,4-MDI),2,2′-diisocyanatodiphenylmethane (2,2-MDI), diphenylmethane diisocyanate(MDI), 3,3′-dimethyl-4,4′-biphenylene isocyanate,3,3′-dimethoxy-4,4′-biphenylene diisocyanate,1-[(2,4-diisocyanatophenyl)methyl]-3-isocyanato-2-methyl benzene, and2,4,6-triisopropyl-m-phenylene diisocyanate.

Isocyanate-terminated urethane-containing adducts may be prepared, forexample, by reacting a hydroxyl-terminated sulfur-containing adduct,such as the hydroxyl-terminated polythioethers of Formula (10a) andFormula (10b) with a compound having a terminal isocyanate group and agroup that is reactive with the terminal hydroxyl groups of thehydroxyl-terminated polythioethers of Formula (10a) and Formula (10b),such as a diisocyanate.

Isocyanate-terminated urethane-containing polythioether adducts may beprepared, for example, by reacting a hydroxyl-terminated polythioetheradduct of Formula (10a) and/or Formula (10b) with a diisocyanate such asTDI, Isonate™ 143L (polycarbodiimide-modified diphenylmethenediisocyanate), Desmodur® N3400 (1,3-diazetidine-2,4-dione,1,3-bis(6-isocyanatohexyl)-), IDPI (isophorone diisocyanate), orDesmodur® W (H₁₂MDI) optionally in the presence of a catalyst such asdibutyltin dilaurate at a temperature from 70° C. to 80° C. to providethe corresponding isocyanate-terminated urethane-containingpolythioether adduct.

A moiety —C(═O)—NH—R²⁰—NH—C(═O)— can be derived from a diisocyanate ofFormula (12):

O═C═N—R²⁰—N═C═O  (12)

In moieties of Formula (20), R²⁰ can be a core of an aliphaticdiisocyanate such as 4,4′-methylene dicyclohexyl diisocyanate and hasthe structure of Formula (13):

A diisocyanate can comprise a cycloaliphatic diisocyanate such as, forexample, 4,4′-methylene dicyclohexyl diisocyanate.

An isocyanate-terminated urethane-containing prepolymer can comprise anisocyanate-terminated urethane-containing prepolymer of Formula (14a),an isocyanate-terminated urethane-containing prepolymer of Formula(14b), or a combination thereof:

O═C═N—R²⁰—NH—C(═O)—[—R⁶⁰—C(═O)—NH—R²⁰—NH—C(═O)—]_(w)—R⁶⁰—C(═O)—NH—R²⁰—N═C═O  (14a)

B{—V′—S—R⁵⁰—S—(CH₂)₂—O—R¹³—O—[—C(═O)—NH—R²⁰—NH—C(═O)—R⁶⁰—]_(w)—C(═O)—NH—R²⁰—N═C═O}_(z)  (14b)

wherein,

-   -   w is an integer from 1 to 100;    -   each R¹³ independently comprises C₂₋₁₀ alkanediyl;    -   each R²⁰ independently comprises a core of a diisocyanate;    -   each R⁵⁰ independently comprises a core of a sulfur-containing        prepolymer;    -   each R⁶⁰ independently comprises a moiety having the structure        of Formula (3):

—O—R¹³—O—(CH₂)₂—S—R⁵⁰—S—(CH₂)₂—O—R¹³—O—  (3)

-   -   B represents a core of a z-valent, polyfunctionalizing agent        B(—V)_(z) wherein,        -   z is an integer from 3 to 6; and        -   each V is a moiety comprising a terminal group reactive with            a thiol group; and    -   each —V′— is derived from the reaction of —V with a thiol.

In prepolymers of Formula (14a) and Formula (14b), each R⁵⁰ can bederived from a polythioether. For example, each R⁵⁰ can have thestructure of Formula (5):

—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—  (5)

-   -   wherein,        -   each R¹ independently is selected from C₂₋₁₀ alkanediyl,            C₆₋₈ cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, C₅₋₈            heterocycloalkanediyl, and            —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—, wherein:            -   p is an integer from 2 to 6;            -   q is an integer from 1 to 5;            -   r is an integer from 2 to 10;            -   each R³ is independently selected from hydrogen and                methyl; and            -   each X is independently selected from —O—, —S—, and                —NR—, wherein R is selected from hydrogen and methyl;        -   each R² is independently selected from C₁₋₁₀ alkanediyl,            C₆₋₈ cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, and            —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—, wherein p, q, r, R³,            and X are as defined as for R¹;        -   m is an integer from 0 to 50;        -   n is an integer from 1 to 60; and        -   s is an integer from 2 to 6.

In prepolymers of Formula (14a) and Formula (14b), w can be an integerfrom 1 to 50, from 2 to 50, or from 1 to 20 or from 2 to 20.

An isocyanate-terminated urethane-containing adduct can comprise thereaction product of reactants comprising a hydroxyl-terminatedsulfur-containing adduct and a diisocyanate.

An isocyanate-terminated urethane-containing adduct can comprise thereaction product of reactants comprising hydroxyl-terminated Permapol®3.1E and a diisocyanate such as a cycloaliphatic diisocyanate.

Isocyanate-terminated urethane-containing adducts may be synthesized byreacting, for example, a diisocyanate with an appropriately terminatedsulfur-containing adduct such as, for example, a hydroxyl-terminatedsulfur-containing adduct, at a suitable temperature such as from 50° C.to 100° C. for a suitable time such as from 1 hour to 4 hours, in thepresence of a tin catalyst, such as dibutyltin dilaurate. Those skilledin the art can determine appropriate reaction conditions.

A moisture-curable urethane-containing prepolymer can comprise thereaction product of reactants comprising an isocyanate-terminatedurethane-containing prepolymer and a compound containing a groupreactive with an isocyanate group and at least one polyalkoxysilylgroup. A compound can comprise one polyalkoxysilyl group, twopolyalkoxysilyl groups, or three polyalkoxysilyl groups.

Groups reactive with isocyanate groups include hydroxyl groups, aminegroups, and thiol groups.

Polyalkoxysilyl groups include groups having the structure of Formula(1):

—Si(—R⁷)_(x)(—OR⁷)_(3-x)  (1)

where R⁷ and x are defined herein.

A compound having groups reactive with isocyanate groups and havingpolyalkoxysilyl groups can comprise an aminosilane.

A compound having at least one terminal polyalkoxysilyl group can havethe structure of Formula (15a) or the structure of Formula (15b):

NH₂(—R⁹—Si(—R⁷)_(x)(—OR⁷)_(3-x))(15a)

NH(—R⁹—Si(—R⁷)_(x)(—OR⁷)_(3-x))₂  (15b)

where x and R⁷ are defined herein, and each R⁹ can independently beselected from C₂₋₆ alkanediyl. A compound of Formula (15a) can have thestructure of Formula (15c):

NH₂—(CH₂)₃—Si(—OCH₃)₃  (15c)

An isocyanate-terminated urethane-containing adduct can be reacted witha compound having a terminal primary amine group and a polyalkoxysilylgroup. Examples of such compounds include[3-(2-aminoethylamino)propyl]trimethoxysilane,3-aminopropyl(diethoxy)methylsilane, (3-aminopropyl)triethoxysilane, and(3-aminopropyl)trimethoxysilane.

An isocyanate-terminated urethane-containing adduct can be reacted witha compounds having a secondary amine and two polyalkoxysilyl groups.Examples of such compounds include bis[3-(trimethoxysilyl)propyl]amine,bis[3-(triethoxysilyl)propyl]amine,N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, δ-aminohexyltrimethoxysilane, and δ-aminohexyl methyldimethoxysilane.

An isocyanate-terminated urethane-containing adduct can be reacted withat least one compound having a terminal primary amine group and apolyalkoxysilyl group and/or at least one compound having a primaryamine group and two polyalkoxysilyl groups.

Moisture-curable prepolymers can be prepared in a three-step reaction.An example of a three-step reaction sequence involves reacting athiol-terminated sulfur-containing prepolymer with a hydroxyl-functionalprepolymer, to provide a hydroxyl-terminated sulfur-containingprepolymer to provide an isocyanate-terminated urethane-containingpolymers, followed by capping the terminal isocyanate groups of theisocyanate-terminated urethane-containing prepolymer withpolyalkoxysilyl groups. One skilled in the art will appreciate thatother chemistries can be employed to synthesize the disclosedprepolymers. Thus, synthetic methods, precursors and intermediates asappropriate provided that the moisture-curable prepolymer comprises aurethane- and sulfur-containing backbone capped with a polyalkoxysilylgroups.

In a first step, a thiol-terminated sulfur-containing prepolymer can bereacted with an ethylenically unsaturated alcohol such as a hydroxyvinyl ether to provide a hydroxyl-terminated sulfur-containing adduct.The reaction can be performed at elevated temperature in the presence ofa free-radical catalyst.

In a second step, the hydroxyl-terminated sulfur-containing adduct canbe reacted with a polyisocyanate to provide an isocyanate-terminatedurethane-containing adduct. The reaction can be performed at elevatedtemperature in the presence of a tin catalyst.

In a third step, the isocyanate-terminated urethane-containing adductcan be reacted with a silane to provide a polyalkoxysilyl-terminatedprepolymer of the present disclosure. The reaction can be performed atroom temperature.

An example of a suitable reaction sequence is provided as follows:

where w, x, R⁷, R⁹, R¹³, R²⁰, R³⁰, R⁵⁰, and R⁶⁰ are defined herein. Anexample of a reaction sequence is shown in FIG. 1. The reaction sequenceillustrated above and in FIG. 1 begins with the reaction of a dithiol.Thiol A can include, for example, a polythiol such as a trithiol, or amixture of polythiols such as a combination of dithiols and trithiols.

Moisture-curable prepolymers provided by the present disclosure may beused in compositions. A composition may be formulated as a sealant, suchas an aerospace sealant. Compositions may further include additives,catalysts, fillers, and/or other sulfur-containing prepolymers includingfor example, polythioethers, polyformals, and/or polysulfides.

Compositions provided by the present disclosure are moisture-curable. Itcan be appreciated that because the curing agent forpolyalkoxysilyl-terminated prepolymers can be atmospheric moisture, itis not necessary to include a curing agent in a curable compositioncontaining a polyalkoxysilyl-terminated prepolymer. Therefore,compositions comprising polyalkoxysilyl-terminated prepolymers providedby the present disclosure and a curing agent for the polyalkoxysilylgroup refer to atmospheric moisture. Compositions provided by thepresent disclosure may include encapsulated water in which applicationof energy can facilitate release of water from an encapsulant to cure orto accelerate curing of the composition.

Polyalkoxysilyl-terminated prepolymers provided by the presentdisclosure can hydrolyze in the presence of water inducingself-polymerization via condensation. A composition can include amoisture cure catalyst. Suitable moisture cure catalysts for use withpolyalkoxysilyl-terminated prepolymers include organotitanium compoundssuch as tetraisopropoxy titanium, tetra-tert-butoxy titanium, titaniumdi(isopropoxy)bis(ethylacetoacetate), and titaniumdi(isopropoxy)bis(acetylacetoacetate); organic tin compounds dibutyltindilaurate, dibutyltin bisacetylacetoacetate, and tin octylate; metaldicarboxylates such as lead dioctylate; organozirconium compounds suchas zirconium tetraacetylacetonate; and organoaluminum compounds such asaluminum triacetyl-acetonate. Other examples of suitable catalysts formoisture curing include diisopropoxy bis(ethylacetoacetonate)titanium,diisopropoxy bis(acetylacetonate)titanium, and dibutoxy bis(methylacetoacetonate)titanium.

A moisture cure catalyst can be a controlled release moisture curecatalyst. A controlled release moisture cure catalyst has little or noactivity until released, such as chemically and/or physically.

A controlled release moisture cure catalyst can comprise a controlledrelease tin catalyst including any of the organo-titanium, organo-tin ororgano-zirconium compounds disclosed herein. A controlled releasemoisture cure catalyst may be an organo-tin catalyst such as dibutyltindilaurate.

Compositions may comprise one or more different types ofcontrolled-release moisture cure catalyst.

When released, controlled release moisture cure catalysts provided bythe present disclosure can catalyze the reaction between moisture/waterand the terminal polyalkoxysilyl groups of thepolyalkoxysilyl-terminated urethane-containing sulfur-containingprepolymer.

In controlled release compositions provided by the present disclosure,the pot life or working time of a composition can be greater than 2weeks if the catalyst is not released. When the catalyst is released,either by chemical, photochemical, physical or other mechanism, the curetime can be less than 72 hours, less than 60 hours, less than 48 hours,less than 36 hours, or less than 24 hours. The cure time without heatingand in the presence of ambient moisture, can be several days such as,for example, 7 days.

A controlled release moisture cure catalyst can comprise a matrixencapsulant. Matrix encapsulation is a process by which droplets orparticles of liquid or solid material are trapped among side chains of acrystalline or semi-crystalline polymer. With increased temperature, thecrystalline polymer becomes amorphous and releases the droplets orparticles into the medium. Matrix encapsulants provided by the presentdisclosure can comprise a crystalline matrix material incorporatingdroplets or particles comprising a moisture cure catalyst. Thus, therate of reaction is to some extent controlled by thermally dependentdiffusion of the moisture cure catalyst from the crystalline polymer.The crystalline polymers may have a sharp well-defined melting point ormay exhibit a melting point range. The use of waxy polymers for matrixencapsulation of catalysts is disclosed in U.S. Application PublicationNo. 2007/0173602.

Examples of suitable matrix encapsulants include Intelimer® polymers(Air Products), such as Intelimer® 13-1 and Intelimer® 13-6. Theproperties of Intelimer® polymers is disclosed, for example, in Lowry etal., Cure evaluation of Intelimer® latent curing agents for thermosetresin applications, presented at the Thermoset Resin FormulatorsAssociation Meeting, Chicago, Ill., Sep. 15-16, 2008.

A matrix encapsulant may be selected to release the moisture curecatalyst following a brief high temperature exposure such as for lessthan 10 minutes, less than 5 minutes, or less than 2 minutes.

During this brief temperature excursion, the moisture cure catalyst isreleased from the matrix and diffuses into the reactive prepolymer suchas applicable here, the polyalkoxysilyl-terminated urethane-containingsulfur-containing prepolymer. The composition may be heated during thecuring process or may be left at ambient temperature. When left atambient temperature, the released moisture cure catalyst composition maycure in less than 2 hours, in less than 4 hours, or in less than 6hours.

Moisture cure catalysts may be incorporated into a matrix encapsulant byblending at a temperature above the melt temperature of the matrixencapsulant, rapidly cooling the mixture, and grinding the solid to apowder. An average particle size can be less than 200 μm, less than 150μm, less than 100 μm, less than 50 μm, or less than 25 μm.

A curable composition may comprise from 0.1 wt % to 25 wt %, from 1 wt %to 15 wt %, or from 5 wt % to 10 wt % of a matrix encapsulant comprisinga moisture cure catalyst. This correlates to 0.01 wt % to 2 wt %, from0.05 wt % to 1.5 wt %, or from 0.5 wt % to 1 wt % of an amine catalyst.

A matrix encapsulant suitable for use in compositions provided by thepresent disclosure can comprise a ratio (wt %/wt %) of wt % a moisturecure catalyst to wt % matrix polymer from 1 to 15, from 2 to 10, or from5 to 8.

Other suitable controlled release encapsulation systems includemicroencapsulation such as core/shell encapsulants and inclusioncatalysts. An example of a core/shell encapsulant comprises a shellsurrounding a catalyst. The catalyst can be released form the shell bythe application of energy such as heat and/or mechanical force. Themechanical force can be the result of the application procedure, amixing process, or both. The shell can comprise a porous material suchthat the encapsulated catalyst can be slowly released over time with orwithout the application of energy. The encapsulating system can alsocomprise a catalyst entrapped in a porous substrate and the poroussubstrate can be surrounded by a polymeric shell. When the shell iscompromised such as during the application of energy, the entrappedcatalyst can then diffuse from the porous substrate. An example of thistechnology includes an encapsulated lipoparticle. Suitable examplesinclude Lipocapsules™ available from Lipo Technologies. An encapsulantsystem can have a particle size from 5 μm to 100 μm. The shell cancomprise a synthetic polymer and the porous substrate core can comprisea hydrophobic material.

Compositions provided by the present disclosure can comprise, inaddition to a moisture-curable urethane-containing prepolymer, one ormore additional polyalkoxysilyl-terminated sulfur-containing adducts. Apolyalkoxysilyl-terminated sulfur-containing adduct can be any suitableprepolymer having at least one sulfur atom in the repeating unit,including, but not limited to, polymeric thiols, polythiols, thioethers,polythioethers, sulfur-containing polyformals, and polysulfides. Apolyalkoxysilyl-terminated sulfur-containing adduct can be prepared byreacting an appropriately functionalized sulfur-containing prepolymerwith an appropriately functionalized silane. Polyalkoxysilyl-terminatedsulfur-containing adducts differ from the moisture-curable prepolymersprovided by the present disclosure in not incorporating a diisocyanate.However, an additional moisture-curable prepolymer may contain chelatinggroups or sulfone groups in the sulfur-containing prepolymer backbonesuch as disclosed in U.S. Application Publication Nos. 2014/0275474 and2014/0275461, each of which is incorporated by reference in itsentirety.

Examples of additional sulfur-containing prepolymers useful incompositions provided by the present disclosure include, for example,those disclosed in U.S. Pat. Nos. 6,172,179, 6,509,418, and 7,009,032,each of which is incorporated by reference in its entirety. Compositionsprovided by the present disclosure can comprise a polythioether havingthe structure of Formula (5):

—R¹—[—S—(CH₂)₂—O—[—R²—O—]_(m)—(CH₂)₂—S—R¹—]_(n)—  (5)

wherein R¹ can be selected from a C₂₋₆ alkanediyl, C₆₋₈ cycloalkanediyl,C₆₋₁₀ cycloalkanealkanediyl, —[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)—, and—[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)— in which at least one —CH₂— unit canbe substituted with a methyl group; R² can be selected from C₂₋₆alkanediyl, C₆₋₈ cycloalkanediyl, C₆₋₁₀ cycloalkanealkanediyl, and—[(—CH₂—)_(p)—X—]_(q)—(—CH₂—)_(r)—; X can be selected from O, S, and—NR⁵—, where R⁵ can be selected from hydrogen and methyl; m can be aninteger from 0 to 10; n can be an integer from 1 to 60; p can be aninteger from 2 to 6; q can be an integer from 1 to 5, and r can be aninteger from 2 to 10. Such polythioethers are described in U.S. Pat. No.6,172,179.

The one or more additional sulfur-containing prepolymers may bedifunctional or multifunctional, for example, having from 3 to 6terminal groups, or a mixture thereof.

Compositions provided by the present disclosure can comprise from 10 wt% to 90 wt % of a sulfur-containing prepolymer provided by the presentdisclosure, from 20 wt % to 80 wt %, from 30 wt % to 70 wt %, or from 40wt % to 60 wt %, where wt % is based on the total weight of allnon-volatile components of the composition (i.e., the dry weight).

An additional sulfur-containing prepolymer can comprise a polysulfide. Apolysulfide refers to a prepolymer that contains one or more sulfidelinkages, i.e., —S_(x)— linkages, where x is from 2 to 4, in theprepolymer backbone and/or in pendant positions on the prepolymer chain.A polysulfide prepolymer can have two or more sulfur-sulfur linkages.Suitable polysulfides are commercially available, for example, from AkzoNobel and Toray Fine Chemicals under the names Thiokol-LP andThioplast®. Thioplast® products are available in a wide range ofmolecular weights ranging, for example, from less than 1,100 to over8,000, with molecular weight being the average molecular weight in gramsper mole. In some cases, the polysulfide has a number average molecularweight of 1,000 Daltons to 4,000 Daltons. The crosslink density of theseproducts also varies, depending on the amount of crosslinking agentused. The —SH content, i.e., thiol or mercaptan content, of theseproducts can also vary. The mercaptan content and molecular weight ofthe polysulfide can affect the cure speed of the polymer, with curespeed increasing with molecular weight.

Sulfur-containing polyformal prepolymers useful in aerospace sealantapplications are disclosed, for example, in U.S. Application PublicationNos. 2012/0234205 and 2012/0238707, each of which is incorporated byreference in its entirety.

An additional sulfur-containing prepolymer can be selected from apolythioether and a polysulfide, and a combination thereof. Asulfur-containing polymer can comprise a polythioether, or asulfur-containing prepolymer can comprise a polysulfide. Asulfur-containing prepolymer may comprise a mixture of differentpolythioethers and/or polysulfides, and the polythioethers and/orpolysulfides may have the same or different functionality. Asulfur-containing prepolymer can have an average functionality from 2 to6, from 2 to 4, from 2 to 3, or from 2.05 to 2.5. For example, asulfur-containing prepolymer can be selected from a difunctionalsulfur-containing prepolymer, a trifunctional sulfur-containingprepolymer, and a combination thereof.

Compositions provided by the present disclosure can comprise one or morethan one adhesion promoter. A one or more adhesion promoter may bepresent in amount from 0.1 wt % to 15 wt % of a composition, less than 5wt %, less than 2 wt %, or less than 1 wt %, based on the total dryweight of the composition. Examples of adhesion promoters includephenolics, such as Methylon® phenolic resin, and organosilanes, such asepoxy, mercapto or amino functional silanes, such as Silquest® A-187 andSilquest® A-1100. Other useful adhesion promoters are known in the art.

A composition provided by the present disclosure can comprise anethylenically unsaturated silane, such as, for example, asulfur-containing ethylenically unsaturated silane, which can improvethe adhesion of a cured sealant to a metal substrate. As used herein,the term sulfur-containing ethylenically unsaturated silane refers to amolecular compound that comprises, within the molecule, (i) at least onesulfur (S) atom, (ii) at least one, in some cases at least two,ethylenically unsaturated carbon-carbon bonds, such as a carbon-carbondouble bonds (C═C); and (iii) at least one silane group,—Si(—R)_(m)(—OR)_(3-m), where each R is independently selected fromhydrogen, alkyl, cycloalkyl, aryl, and others, and m is selected from 0,1, and 2. Examples of ethylenically unsaturated silanes are disclosed inU.S. Application Publication No. 2012/0040104, which is incorporated byreference in its entirety.

Compositions provided by the present disclosure may comprise one or moredifferent types of filler. Suitable fillers include those commonly knownin the art, including inorganic fillers, such as carbon black andcalcium carbonate (CaCO₃), silica, polymer powders, and lightweightfillers. Suitable lightweight fillers include, for example, thosedescribed in U.S. Pat. No. 6,525,168. A composition can include 5 wt %to 60 wt % of the filler or combination of fillers, 10 wt % to 50 wt %,or from 20 wt % to 40 wt %, based on the total dry weight of thecomposition. Compositions provided by the present disclosure may furtherinclude one or more colorants, thixotropic agents, accelerators, fireretardants, adhesion promoters, solvents, masking agents, or acombination of any of the foregoing. As can be appreciated, fillers andadditives employed in a composition may be selected so as to becompatible with each other as well as the polymeric component, curingagent, and or catalyst.

Compositions provided by the present disclosure can include low densityfiller particles. As used herein, low density, when used with referenceto such particles means that the particles can have a specific gravityof no more than 0.7, or no more than 0.25, or no more than 0.1. Suitablelightweight filler particles often fall within twocategories—microspheres and amorphous particles. The specific gravity ofmicrospheres may range from 0.1 to 0.7 and include, for example,polystyrene foam, microspheres of polyacrylates and polyolefins, andsilica microspheres having particle sizes ranging from 5 to 100 micronsand a specific gravity of 0.25 (Eccospheres®). Other examples includealumina/silica microspheres having particle sizes in the range of 5 to300 microns and a specific gravity of 0.7 (Fillite®), aluminum silicatemicrospheres having a specific gravity of from 0.45 to 0.7 (Z-Light®),calcium carbonate-coated polyvinylidene copolymer microspheres having aspecific gravity of 0.13 (Dualite® 6001AE), and calcium carbonate coatedacrylonitrile copolymer microspheres such as Dualite® E135, having anaverage particle size of t 40 μm and a density of 0.135 g/cc (Henkel).Suitable fillers for decreasing the specific gravity of the compositioninclude, for example, hollow microspheres such as Expancel® microspheres(available from AkzoNobel) or Dualite® low density polymer microspheres(available from Henkel). Compositions provided by the present disclosurecan include lightweight filler particles comprising an exterior surfacecoated with a thin coating, such as those described in U.S. PublicationNo. 2010/0041839, which is incorporated by reference in its entirety.

A low density filler can comprise less than 2 wt % of a composition,less than 1.5 wt %, less than 1.0 wt %, less than 0.8 wt %, less than0.75 wt %, less than 0.7 wt % or less than 0.5 wt % of a composition,where wt % is based on the total dry solids weight of the composition.

Compositions provided by the present disclosure can comprise at leastone filler that is effective in reducing the specific gravity of thecomposition. The specific gravity of a composition can be from 0.8 to 1,0.7 to 0.9, from 0.75 to 0.85, or can be 0.8. The specific gravity of acomposition can be less than 0.9, less than 0.8, less than 0.75, lessthan 0.7, less than 0.65, less than 0.6, or less than 0.55.

A thiol-terminated polythioether including a combination ofthiol-terminated polythioethers can comprise from 50 wt % to 90 wt % ofa composition, from 60 wt % to 90 wt %, from 70 wt % to 90 wt %, or from80 wt % to 90 wt % of the composition, where wt % is based on the totaldry solids weight of the composition.

A composition may also include any number of additives as desired.Examples of suitable additives include plasticizers, pigments,surfactants, adhesion promoters, thixotropic agents, fire retardants,masking agents, and combinations of any of the foregoing. When used, theadditives may be present in a composition in an amount ranging, forexample, from 0% to 60% by weight. Additives may be present in acomposition in an amount ranging from 25% to 60% by weight.

Compositions provided by the present disclosure may be used, forexample, in sealants, coatings, encapsulants, and potting compositions.A sealant includes a composition capable of producing a film that hasthe ability to resist operational conditions, such as moisture andtemperature, and at least partially block the transmission of materials,such as water, fuel, and other liquid and gases. A coating compositionincludes a covering that is applied to the surface of a substrate to,for example, improve the properties of the substrate such as theappearance, adhesion, wettability, corrosion resistance, wearresistance, fuel resistance, and/or abrasion resistance. A pottingcomposition includes a material useful in an electronic assembly toprovide resistance to shock and vibration and to exclude moisture andcorrosive agents. Sealant compositions provided by the presentdisclosure are useful, e.g., as aerospace sealants and as linings forfuel tanks.

Compositions containing moisture-curable urethane-containing prepolymerscan be formulated as sealants.

Compositions containing polyalkoxysilyl-terminated urethane-containingprepolymers and controlled release moisture cure catalysts can beprepared as one-part formulation. The one-part formulation can be sealedto inhibit or prevent exposure to moisture. In use, the formulation canbe applied to a surface at which time the formulation will be exposed toatmospheric moisture and begin curing to some extent. Energy in the formof temperature or impact can be applied to the sealant to cause themoisture cure catalyst to be released from the encapsulant. The releasedmoisture cure catalyst accelerates curing of thepolyalkoxysilyl-terminated urethane-containing prepolymer in thepresence of moisture to provide a cured sealant.

Compositions, including sealants, provided by the present disclosure maybe applied to any of a variety of substrates. Examples of substrates towhich a composition may be applied include metals such as titanium,stainless steel, and aluminum, any of which may be anodized, primed,organic-coated or chromate-coated, epoxy; urethane, graphite, fiberglasscomposite, Kevlar®, acrylics, and polycarbonates.

Compositions provided by the present disclosure may be applied to acoating on a substrate, such as a polyurethane coating.

Compositions provided by the present disclosure may be applied directlyonto the surface of a substrate or over an underlayer by any suitablecoating process known to those of ordinary skill in the art.

Furthermore, methods are provided for sealing an aperture, a part, or asurface utilizing a composition provided by the present disclosure.These methods comprise, for example, applying a composition provided bythe present disclosure to a surface to seal an aperture, part, orsurface, and curing the composition. A method for sealing an aperturecan comprise (a) applying a sealant composition provided by the presentdisclosure to one or more surfaces defining an aperture, (b) assemblingthe surfaces defining the aperture, and (c) curing the sealant, toprovide a sealed aperture, part, or surface.

A composition may be cured under ambient conditions, where ambientconditions refers to a temperature from 20° C. to 25° C., andatmospheric humidity. A composition may be cured under conditionsencompassing a temperature from a 0° C. to 100° C. and humidity from 0%relative humidity to 100% relative humidity. A composition may be curedat a higher temperature such as at least 30° C., at least 40° C., or atleast 50° C. A composition may be cured at room temperature, e.g., 25°C. A composition may be cured upon exposure to actinic radiation, suchas ultraviolet radiation. As will also be appreciated, the methods maybe used to seal apertures on aerospace vehicles including aircraft andaerospace vehicles. Curing can include methods in which energy such asheat is applied to a curable composition to promote curing, methods inwhich a curable composition is left to cure at ambient atmosphericconditions, and combinations thereof,

A composition can achieve a tack-free cure in less than 6 hours, in lessthan 12 hours, less than 18 hours, less than 24 hours, or less than a 48hours, after the useful working time of the composition.

The time to form a viable seal using curable compositions of the presentdisclosure can depend on several factors as can be appreciated by thoseskilled in the art, and as defined by the requirements of applicablestandards and specifications. In general, curable compositions of thepresent disclosure develop adhesion strength within 24 hours to 30hours, and 90% of full adhesion strength develops from 2 days to 3 days,following application to a surface. In general, full adhesion strengthas well as other properties of cured compositions of the presentdisclosure becomes fully developed within 7 days following mixing andapplication of a curable composition to a surface.

For aerospace sealant applications it can be desirable that a sealantmeet the requirements of Mil-S-22473E (Sealant Grade C) at a curedthickness of 20 mils, exhibit an elongation greater than 200%, a tensilestrength greater than 250 psi, and excellent fuel resistance, andmaintain these properties over a wide temperature range from −67° F. to360° F. In general, the visual appearance of the sealant is not animportant attribute. Prior to cure, it can be desirable that the mixedcomponents have a useful working time or pot life of at least 24 hoursand have a cure time within 24 hours of the pot life. Useful workingtime or pot life refers to the time the composition remains workable forapplication at ambient temperatures and exposure to moisture, such asambient atmospheric moisture. Compositions provided by the presentdisclosure, following exposure to moisture, can have a pot life of atleast 6 hours, at least 12 hours, at least 18 hours, at least 24 hours,or more than 24 hours. Compositions provided by the present disclosurecan cure in less than 6 hours after the pot life, in less than 12 hours,in less than 18 hours, in less than 24 hours, in less than 48 hours, orin less than 72 hours after useful working time.

Compositions of the present disclosure can have a shelf life of at least1 month, at least 4 months, at least 6 months, or greater than 6 months,when stored under moisture-free conditions.

Compositions, including sealants, provided by the present disclosure maybe applied to any of a variety of substrates. Examples of substrates towhich a composition may be applied include metals such as titanium,stainless steel, and aluminum, any of which may be anodized, primed,organic-coated or chromate-coated, epoxy, urethane, graphite, fiberglasscomposite, Kevlar®, acrylics, and polycarbonates. Compositions providedby the present disclosure may be applied to a coating on a substrate,such as a polyurethane coating.

Compositions provided by the present disclosure may be applied directlyonto the surface of a substrate or over an underlayer by any suitablecoating process known to those of ordinary skill in the art.

Furthermore, methods are provided for sealing an aperture utilizing acomposition provided by the present disclosure. These methods comprise,for example, applying a composition provided by the present disclosureto a surface to seal an aperture, and curing the composition. A methodfor sealing an aperture can comprise applying a sealant compositionprovided by the present disclosure to defining surface of an apertureand curing the sealant, to provide a sealed aperture.

A composition may be cured under ambient conditions, where ambientconditions refers to a temperature from 20° C. to 25° C., andatmospheric humidity. A composition may be cured under conditionsencompassing a temperature from a 0° C. to 100° C. and humidity from 0%relative humidity to 100% relative humidity. A composition may be curedat a higher temperature such as at least 30° C., at least 40° C., or atleast 50° C. A composition may be cured at room temperature, e.g., 25°C. A composition may be cured upon exposure to actinic radiation, suchas ultraviolet radiation. As will also be appreciated, the methods maybe used to seal apertures on aerospace vehicles including aircraft andaerospace vehicles.

A composition can achieve a tack-free cure in less than 2 hours, lessthan 4 hours, less than 6 hours, less than 8 hours, or less than 10hours, at a temperature of less than 200° F., less than 100° F., lessthan 80° F., or less than 60° F.

The time to form a viable seal using curable compositions of the presentdisclosure can depend on several factors as can be appreciated by thoseskilled in the art, and as defined by the requirements of applicablestandards and specifications. In general, curable compositions of thepresent disclosure develop adhesion strength within 24 hours to 30hours, and 90% of full adhesion strength develops from 2 days to 3 days,following mixing and application to a surface. In general, full adhesionstrength as well as other properties of cured compositions of thepresent disclosure becomes fully developed within 7 days followingmixing and application of a curable composition to a surface.

Cured compositions disclosed herein, such as cured sealants, can exhibitproperties acceptable for use in aerospace applications. In general, itcan be desirable that sealants used in aviation and aerospaceapplications exhibit the following properties: peel strength greaterthan 20 pounds per linear inch (pli) on Aerospace Material Specification(AMS) 3265B substrates determined under dry conditions, followingimmersion in JRF Type I for 7 days, and following immersion in asolution of 3% NaCl according to AMS 3265B test specifications; tensilestrength between 300 pounds per square inch (psi) and 400 psi; tearstrength greater than 50 pounds per linear inch (pli); elongationbetween 250% and 300%; and hardness greater than 40 Durometer A. Theseand other cured sealant properties appropriate for aviation andaerospace applications are disclosed in AMS 3265B, the entirety of whichis incorporated herein by reference. It is also desirable that, whencured, compositions of the present disclosure used in aviation andaircraft applications exhibit a percent volume swell not greater than25% following immersion for one week at 60° C. (140° F.) and ambientpressure in JRF Type I. Other properties, ranges, and/or thresholds maybe appropriate for other sealant applications.

Compositions provided by the present disclosure can be fuel-resistant.As used herein, the term “fuel resistant” means that a composition, whenapplied to a substrate and cured, can provide a cured product, such as asealant, that exhibits a percent volume swell of not greater than 40%,in some cases not greater than 25%, in some cases not greater than 20%,in yet other cases not more than 10%, after immersion for one week at140° F. (60° C.) and ambient pressure in Jet Reference Fluid (JRF) TypeI according to methods similar to those described in ASTM D792 (AmericanSociety for Testing and Materials) or AMS 3269 (Aerospace MaterialSpecification). JRF Type I, as employed for determination of fuelresistance, has the following composition: toluene: 28%±1% by volume;cyclohexane (technical): 34%±1% by volume; isooctane: 38%±1% by volume;and tertiary dibutyl disulfide: 1%±0.005% by volume (see AMS 2629,issued Jul. 1, 1989, §3.1.1 etc., available from SAE (Society ofAutomotive Engineers)).

Compositions provided herein can provide a cured product, such as asealant, exhibiting a tensile elongation of at least 100% and a tensilestrength of at least 400 psi when measured in accordance with theprocedure described in AMS 3279, §3.3.17.1, test procedure AS5127/1,§7.7.

Compositions can provide a cured product, such as a sealant, thatexhibits a lap shear strength of greater than 200 psi, such as at least220 psi, at least 250 psi, and, in some cases, at least 400 psi, whenmeasured according to the procedure described in SAE AS5127/1 paragraph7.8.

A cured sealant comprising a composition provided by the presentdisclosure can meet or exceed the requirements for aerospace sealants asset forth in AMS 3277.

Compositions provided by the present disclosure, when cured, can exhibita Shore A hardness (following 7-day cure) greater than 10, greater than20, greater than 30, or greater than 40; a tensile strength greater than10 psi, greater than 100 psi, greater than 200 psi, or greater than 500psi; an elongation greater than 100%, greater than 200%, greater than500%, or greater than 1,000%; and a swell following exposure to JRF TypeI (7 days) less than 20%.

Tensile strength and elongation may be determined according to ASTM412C.

EXAMPLES

Embodiments provided by the present disclosure are further illustratedby reference to the following examples, which describe the synthesis,properties, and uses of certain prepolymers and compositions provided bythe present disclosure. It will be apparent to those skilled in the artthat many modifications, both to materials, and methods, may bepracticed without departing from the scope of the disclosure.

Example 1 Synthesis of Thiol-Terminated Polythioether Adduct

A thiol-terminated polythioether was prepared according to Example 1 ofU.S. Pat. No. 6,172,179. In a 2-L flask, 524.8 g (3.32 mol) ofdiethylene glycol divinyl ether (DEG-DVE) and 706.7 g (3.87 mol) ofdimercaptodioxaoctane (DMDO) were mixed with 19.7 g (0.08 mol) oftriallylcyanurate (TAC) and heated to 77° C. To the reaction mixture wasadded 4.6 g (0.024 mol) of an azobisnitrile free radical catalyst(Vazo®-67, 2,2′-azobis(2-methylbutyronitrile)). The reaction proceededsubstantially to completion after 2 hours to afford 1,250 g (0.39 mol,yield 100%) of a liquid thiol-terminated polythioether adduct having aT_(g) of −68° C. and a viscosity of 65 poise. The adduct was faintlyyellow and had low odor.

Example 2 Synthesis of H₁₂MDI-Terminated Urethane-Containing Prepolymer

A 1-liter, 4-neck round-bottomed flask was fitted with a mantle,thermocouple, temperature controller, nitrogen line, mechanical stirrerand dropping funnel. The flask was charged with a thiol-terminatedpolythioether (652.30 g) prepared according to Example 1. The flask washeated to 71° C. under nitrogen and stirred at 300 rpm. A mixture of4-hydroxybutyl vinyl ether (47.40 g) and Vazo®-67 (1.19 g) was added tothe flask in 1 hour via a dropping funnel. The reaction mixture wasmaintained at 71° C. for 41 hours, at which time the reaction wascomplete. After this, the reaction apparatus was fitted with a vacuumline and the product heated to 94° C. Heating was continued for 1.3hours under vacuum. Following vacuum treatment, a pale yellow, viscouspolythioether polyol (678.80 g) was obtained. The polythioether polyolhad a hydroxyl number of 31.8 and a viscosity of 77 Poise.

The polythioether polyol (300.03 g) was then charged into a 500-mL,4-neck, round-bottom flask. The flask was equipped with a mantle,thermocouple, temperature controller, an inlet for providing nitrogenpositive pressure, and a mechanical stirrer (PTFE paddle and bearing).The polythioether polyol was stirred at ca. 200 rpm and heated to 76.6°C. (170° F.), followed by the addition of Desmodur®-W (H₁₂MDI) (82.00 g)and a 0.01% solution of dibutyltin dilaurate dissolved in methyl ethylketone (3.90 g). The reaction mixture was maintained at 76.6° C. for 7 hand then cooled to room temperature. A 1% solution of benzyl chloridedissolved in methyl ethyl ketone (3.80 g) was then added to the reactionmixture. The resulting H₁₂MDI-terminated polythioether prepolymer had anisocyanate content of 3.9%.

Example 3 Synthesis of Polyalkoxysilyl-Terminated Urethane-ContainingPrepolymer

The isocyanate-terminated urethane-containing prepolymer of Example 2(20.00 g), (3-aminopropyl)triethoxysilane (3.00 g), andmethyldimethoxyvinylsilane (4.50 g) were placed in a 60-g Hauschild cupwith a lid. The reactants were mixed for 4 min at 2300 rpm with a DAC600 FVZ Speed Mixer (FlackTek Inc.), and left to sit at room temperaturefor 1 hour. During this time, the isocyanate functionality of theExample 1 prepolymer fully reacted with (3-aminopropyl)triethoxysilane,yielding a polyalkoxysilyl-terminated prepolymer. This was evidenced bythe viscosity increase of the mixture. The methyldimethoxyvinylsilanedimethoxy(methyl)(vinyl)silane) did not participate in the reaction.

Example 4 Formulation of Polyalkoxysilyl-Terminated Urethane-ContainingPrepolymer

Two-hundred (200) μL of water and 200 μL of dibutyltin dilaurate wereadded to the mixture of Example 3 and mixed for 30 seconds at 2300 rpmwith a DAC 600 FVZ Speed Mixer. The mixture was poured out onto acircular, 6-inch in diameter, polycarbonate lid to make tensile andelongation specimens. The specimens were allowed to cure for 3 days, atwhich time the material was fully cured. The tensile and elongationvalues were measured according to ASTM 412C. The tensile strength was451 psi and the elongation was 288%.

Example 5 Synthesis of Polyalkoxysilyl-Terminated Urethane-ContainingPrepolymer

The isocyanate-terminated urethane-containing prepolymer of Example 2(20.00 g), (3-aminopropyl)triethoxysilane (3.02 g), andmethyldimethoxyvinylsilane (4.54 g) were placed in a 60-g Hauschild cup.The reactants were mixed for 4 min at 2300 rpm with a DAC 600 FVZ SpeedMixer, and was left to sit at room temperature for 1 hour. During thistime, the isocyanate functionality of the Example 1 prepolymer fullyreacted with (3-aminopropyl)triethoxysilane, yielding apolyalkoxysilyl-terminated urethane-containing prepolymer. This wasevidenced by the viscosity increase of the mixture. Themethyldimethoxyvinylsilane (dimethoxy(methyl)(vinyl)silane) did notparticipate in the reaction.

Example 6 Formulation of Polyalkoxysilyl-Terminated Urethane-ContainingPrepolymer

Two-hundred (200) μL of water and 200 μL of dibutyltin dilaurate wereadded to the mixture of Example 5 and mixed for 30 seconds at 2300 rpmwith a DAC 600 FVZ Speed Mixer. The mixture was poured out onto acircular, 6-inch in diameter, polycarbonate lid to make tensile andelongation specimens. The specimens were allowed to cure for 3 days, atwhich time the material was fully cured. The tensile and elongationvalues were measured according to ASTM 412C. The tensile strength was400 psi and the elongation was 222%.

Example 7 Additional Formulations

Additional formulations were prepared similar to those in Examples 4 and5 and the tensile strength and elongation of the cured sealantsmeasured. The results are summarized in Table 1 and in Table 2.

TABLE 1 Tensile strength and elongation. Tensile strength (psi)/ % NCO %C Elongation (%) 3.8 20 471/110 3.8 16 675/150

TABLE 2 Tensile strength and elongation. Tensile strength (psi)/ % NCO %A % B % C Elongation (%) 3.8 0 27 0 666/75 3.8 0 11 16  451/288 3.8 1514 0 421/44

In Tables 1 and 2, % NCO refers to the isocyanate content of theprepolymer, A is 3-aminopropyl)triethoxysilane, B is3-(aminopropyl)(methyl)dimethoxysilane, and C ismethoxy(methyl)vinylsilane, where the percent (%) refers to wt % of thetotal solids weight of the composition.

Example 8 Synthesis of a Moisture-Curable Polymer

1,8-Dimercapto-3,6-dioxaoctane (DMDO, 70.28 g, 0.386 mol) and1,5-dimercapto-3-thiapentane (23.75 g, 0.154 mole) were charged into a250-mL, 3-necked round-bottomed flask. The flask was equipped with amechanical stirrer, a temperature probe and a gas adapter. Whilestirring, the contents were evacuated at 10 mm for 10 min. Vacuum wasreleased under nitrogen and the reaction mixture was heated to 60° C.Filtered diethylene glycol divinyl ether (81.31 g, 0.14 mole) was mixedwith a solution of Vazo®-67 (0.088 g) in toluene (½ mL) and theresulting solution was added to the reaction mixture over a period of 5h. The reaction temperature was increased to 70° C. and nine portions ofradical initiator Vazo®-67 (each: 0.034 g; 0.00018 mole) were added atan interval of 1 h to complete the synthesis of a polydithiol ofequivalent weight 3490.

Vinylmethyldimethoxysilane (13.29 g, 0.101 mole) was added into thereaction mixture and heated at 70° C. for 1 hr. The reaction mixture wasfurther heated to 77° C. for 7 h and then to 70° C. for 8 h. Fourteenportions of radical initiator Vazo®-67 (each: 0.032 g; 0.00017 mole)were added at an interval of 1 h at 70° C. to drive the reaction to highconversion (HS No.: 152,225). Excess silane was removed by evacuatingthe reaction mixture at 5 mmHg/70° C. for 2 hr. The isolated product hada viscosity of 178P, and upon standing at room temperature for severaldays, the polymer turned into a very soft wax.

Example 9 Sealant Comprising an Encapsulated Tin Catalyst

The polymer of Example 8 (16.50 g) was charged into a Hauschild mixingcup (size: 60 g) and mixed in a Hauschild mixer (Hauschild Engineering)for 4 min. Calcium carbonate (9.24 g, 60 phr) was added and the contentswere mixed in Hauschild mixer for 30 sec. The contents were hand-mixedand mixed again in the Hauschild mixer for 4 min.

Hexamethyldisilazane-treated silica (0.66 g; 4 phr) was added and thecontents were mixed in a Hauschild mixer for 30 sec. The contents werehand-mixed, then mixed in a Hauschild mixer for 4 min and cooled to roomtemperature. The product was divided equally in two portions, A and B.

Portion A (13.2 g) and 2 phr of encapsulated dibutyltin dilaurateLipocapsules® PMU (0.17 g, Lipo Technologies) were charged into aHauschild mixing cup (size: 60 g). The contents were hand-mixed, thenmixed in a Hauschild mixer for 30 sec, and spread in a pan for curingunder ambient conditions.

Portion B (13.2 g) and 1.29 phr of dibutyltin dilaurate (0.11 g, AirProducts) were charged into a Hauschild mixing cup (size: 60 g). Thecontents were hand-mixed, then mixed in a Hauschild mixer for 30 sec,and spread in a pan for curing under ambient conditions.

The curing progress was monitored by checking the tack-free time and theincrease in hardness. The results are shown in Table 3.

TABLE 3 Curing progress. Curing Curing Curing Progress Curing ProgressPeriod Period (Catalyst: Lipocapsules ® (Catalyst: Dibutyltin (Days)(Hours) PMU) Dilaurate) 0 5 No/low curing No/low curing 1 24 Curing hadprogressed Tack-free Slightly Tacky 2 48 Tack-free Shore A Hardness: 30Shore A Hardness: 10 3 72 30 46 4 96 35 50 5 120 40 51 6 144 44 51 7 16845 51 8 192 45 52

Finally, it should be noted that there are alternative ways ofimplementing the embodiments disclosed herein. Accordingly, the presentembodiments are to be considered as illustrative and not restrictive.Furthermore, the claims are not to be limited to the details givenherein, and are entitled their full scope and equivalents thereof.

What is claimed is:
 1. A composition comprising: (a) a moisture-curableurethane-containing prepolymer comprising a reaction product ofreactants comprising: (i) an isocyanate-terminated urethane-containingadduct comprising the reaction product of reactants comprising: ahydroxyl-terminated sulfur-containing adduct comprising the reactionproduct of reactants comprising a hydroxy vinyl ether and athiol-terminated sulfur-containing prepolymer; and a diisocyanate; and(ii) a compound comprising: a group reactive with an isocyanate group;and at least one polyalkoxysilyl group; and (b) a controlled releasemoisture cure catalyst.
 2. The composition of claim 1, wherein thehydroxyl-terminated sulfur-containing adduct comprises ahydroxyl-terminated polythioether adduct of Formula (10a), ahydroxyl-terminated polythioether adduct of Formula (10b), or acombination thereof:R⁶—S—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—S—R⁶  (10a){R⁶—S—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—S—V′—}_(z)B  (10b)wherein, each R¹ independently is selected from C₂₋₁₀ alkanediyl, C₆₋₈cycloalkanediyl, C₆₋₁₀ alkanecycloalkanediyl, C₅₋₈heterocycloalkanediyl, and —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—,wherein, p is an integer from 2 to 6; q is an integer from 1 to 5; r isan integer from 2 to 10; each R³ is independently selected from hydrogenand methyl; and each X is independently selected from —O—, —S—, and—NR—, wherein R is selected from hydrogen and methyl; each R² isindependently selected from C₁₋₁₀ alkanediyl, C₆₋₈ cycloalkanediyl,C₆₋₁₄ alkanecycloalkanediyl, and —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—,wherein p, q, r, R³, and X are as defined for R¹; m is an integer from 0to 50; n is an integer from 1 to 60; and s is an integer from 2 to 6;each R⁶ is independently selected from —CH₂—CH₂—O—R¹³—OH, wherein eachR¹³ is C₂₋₁₀ alkanediyl; and B represents a core of a z-valent,polyfunctionalizing agent B(—V)_(z) wherein, z is an integer from 3 to6; and each V is a moiety comprising a terminal group reactive with athiol group; and each —V′— is derived from the reaction of —V with athiol.
 3. The composition of claim 1, wherein the thiol-terminatedsulfur-containing prepolymer comprises a thiol-terminated polythioetherprepolymer of Formula (6a), a thiol-terminated polythioether prepolymerof Formula (6b), or a combination thereof:HS—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—SH  (6a){HS—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—S—V′—}_(z)B  (6b)wherein: each R¹ independently is selected from C₂₋₁₀ alkanediyl, C₆₋₈cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, C₅₋₈heterocycloalkanediyl, and —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—,wherein: p is an integer from 2 to 6; q is an integer from 1 to 5; r isan integer from 2 to 10; each R³ is independently selected from hydrogenand methyl; and each X is independently selected from —O—, —S—, and—NR—, wherein R is selected from hydrogen and methyl; each R² isindependently selected from C₁₋₁₀ alkanediyl, C₆₋₈ cycloalkanediyl,C₆₋₁₄ alkanecycloalkanediyl, and —[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—,wherein p, q, r, R³, and X are as defined as for R¹; m is an integerfrom 0 to 50; n is an integer from 1 to 60; s is an integer from 2 to 6;B represents a core of a z-valent, polyfunctionalizing agent B(—V)_(z)wherein: z is an integer from 3 to 6; and each V is a group comprising aterminal group reactive with a thiol group; and each —V′— is derivedfrom the reaction of —V with a thiol.
 4. The composition of claim 1,wherein the isocyanate-terminated urethane-containing adduct comprisesan isocyanate-terminated urethane-containing polythioether, anisocyanate-terminated urethane-containing polysulfide, anisocyanate-terminated urethane-containing sulfur-containing polyformal,or a combination of any of the foregoing.
 5. The composition of claim 1,wherein the compound (ii) comprises an aminosilane.
 6. The compositionof claim 5, wherein the aminosilane comprises(3-aminopropyl)triethoxysilane.
 7. The composition of claim 1,comprising dimethoxy(methyl)(vinyl)silane.
 8. The composition of claim1, formulated as a sealant.
 9. A cured sealant, prepared from thecomposition of claim
 8. 10. A part sealed with the composition of claim8.
 11. A method of sealing a surface, comprising: applying thecomposition of claim 8 to at least a portion of a surface; activatingthe controlled release moisture cure catalyst; and curing the appliedcomposition to seal the surface.
 12. A composition comprising: (a) amoisture-curable urethane-containing prepolymer comprising amoisture-curable urethane-containing prepolymer of Formula (2a), amoisture-curable urethane-containing prepolymer of Formula (2b), or acombination thereof:R³⁰—C(═O)—NH—R²⁰—NH—C(═O)—[—R⁶⁰—C(═O)—NH—R²⁰—NH—C(═O)—]_(w)—R⁶⁰—C(═O)—NH—R²⁰—NH—C(═O)—R³⁰  (2a)B{—V′—S—R⁵⁰—S—(CH₂)₂—O—R¹³—O—[—C(═O)—NH—R²⁰—NH—C(═O)—R⁶⁰—]_(w)—C(═O)—NH—R²⁰—NH—C(═O)—R³⁰}_(z)  (2b)wherein, w is an integer from 1 to 100; each R¹³ independently comprisesC₂₋₁₀ alkanediyl; each R²⁰ independently comprises a core of adiisocyanate; each R³⁰ independently is a moiety comprising a terminalpolyalkoxysilyl group; each R⁵⁰ independently comprises a core of asulfur-containing prepolymer; each R⁶⁰ independently comprises a moietyhaving the structure of Formula (3):—O—R¹³—O—(CH₂)₂—S—R⁵⁰—S—(CH₂)₂—O—R¹³—O—  (3) B represents a core of az-valent, polyfunctionalizing agent B(—V)_(z) wherein, z is an integerfrom 3 to 6; and each V is a moiety comprising a terminal group reactivewith a thiol group; and each —V′— is derived from the reaction of —Vwith a thiol; and (b) a controlled release moisture cure catalyst. 13.The composition of claim 12, wherein each R³⁰ comprises a moiety ofFormula (4a), a moiety of Formula (4b), or a combination thereof:—NH(—R⁹—Si(—R⁷)_(x)(—OR⁷)_(3-x))  (4a)—N(—R⁹—Si(—R⁷)_(x)(—OR⁷)_(3-x))₂  (4b) wherein, x is selected from 0, 1,and 2; each R⁷ is independently selected from C₁₋₄ alkyl; and each R⁹ isindependently C₁₋₆ alkanediyl.
 14. The composition of claim 12, whereineach R⁵⁰ comprises a moiety having the structure of Formula (5):—R¹—[—S—(CH₂)_(s)—O—(R²—O)_(m)—(CH₂)₂—S—R¹—]_(n)—  (5) wherein, each R¹independently is selected from C₂₋₁₀ alkanediyl, C₆₋₈ cycloalkanediyl,C₆₋₁₄ alkanecycloalkanediyl, C₅₋₈ heterocycloalkanediyl, and—[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—, wherein: p is an integer from 2 to6; q is an integer from 1 to 5; r is an integer from 2 to 10; each R³ isindependently selected from hydrogen and methyl; and each X isindependently selected from —O—, —S—, and —NR—, wherein R is selectedfrom hydrogen and methyl; each R² is independently selected from C₁₋₁₀alkanediyl, C₆₋₈ cycloalkanediyl, C₆₋₁₄ alkanecycloalkanediyl, and—[(—CHR³—)_(p)—X—]_(q)—(—CHR³—)_(r)—, wherein p, q, r, R³, and X are asdefined as for R¹; m is an integer from 0 to 50; n is an integer from 1to 60; and s is an integer from 2 to
 6. 15. The composition of claim 12,wherein each R³⁰ is a moiety of Formula (4c):—NH—(CH₂)₃—Si(—OCH₃)₃  (4c)
 16. The composition of claim 12, comprisingdimethoxy(methyl)(vinyl)silane.
 17. The composition of claim 12,formulated as a sealant.
 18. A cured sealant prepared from thecomposition of claim
 17. 19. A part sealed with the composition of claim17.
 20. A method of sealing a surface, comprising: applying thecomposition of claim 17 to at least a portion of a surface; activatingthe controlled release moisture cure catalyst; and curing the appliedcomposition to seal the surface.